diff --git a/.github/workflows/elixir.yml b/.github/workflows/elixir.yml
index 57c6f5bf..3efca605 100644
--- a/.github/workflows/elixir.yml
+++ b/.github/workflows/elixir.yml
@@ -13,41 +13,26 @@ jobs:
     strategy:
       matrix:
         pair:
-          - otp-version: '23.0'
-            elixir-version: '1.13.4'
-          - otp-version: '24.0'
-            elixir-version: '1.13.4'
-          - otp-version: '24.0'
-            elixir-version: '1.14.2'
-          - otp-version: '25.0'
-            elixir-version: '1.13.4'
-          - otp-version: '25.0'
-            elixir-version: '1.14.2'
           - otp-version: '25.1.2'
             elixir-version: '1.15.7'
           - otp-version: '26.0'
             elixir-version: '1.16.0'
+          - otp-version: '27.3.3'
+            elixir-version: '1.18.3'
     steps:
-    - uses: actions/checkout@v2
-    - name: Set up Elixir
-      uses: erlef/setup-beam@988e02bfe678367a02564f65ca2e37726dc0268f
-      env:
-        ImageOS: ubuntu20
-      with:
-        otp-version: ${{matrix.pair.otp-version}}
-        elixir-version: ${{matrix.pair.elixir-version}}
-    - name: Restore dependencies cache
-      uses: actions/cache@v2
-      with:
-        path: deps
-        key: ${{ runner.os }}-mix-${{ hashFiles('**/mix.lock') }}
-        restore-keys: ${{ runner.os }}-mix-
-    - name: Install dependencies
-      run: mix deps.get
-    - name: Run tests
-      run: mix test
-    - name: Run tests with espec
-      run: mix espec
-    - name: Run formatters
-      run: mix espec spec_formatters/test_spec.exs
+      - name: Checkout
+        uses: actions/checkout@v4
+      - name: Set up Elixir and Erlang
+        uses: erlef/setup-beam@v1
+        with:
+          otp-version: ${{matrix.pair.otp-version}}
+          elixir-version: ${{matrix.pair.elixir-version}}
+      - name: Install dependencies
+        run: mix deps.get
+      - name: Run tests
+        run: mix test
+      - name: Run tests with espec
+        run: mix espec
+      - name: Run formatters
+        run: mix espec spec_formatters/test_spec.exs
 
diff --git a/lib/espec/assertions/accepted.ex b/lib/espec/assertions/accepted.ex
index 4ced8312..c377fd8f 100644
--- a/lib/espec/assertions/accepted.ex
+++ b/lib/espec/assertions/accepted.ex
@@ -77,6 +77,9 @@ defmodule ESpec.Assertions.Accepted do
     opts_count = Keyword.get(opts, :count) || :any
     count = if opts_count == :any, do: "at least once", else: "`#{opts_count}` times"
 
-    "Expected `#{inspect(subject)}` #{to} accept `#{inspect(func)}` with `#{inspect(args)}` in process `#{inspect(pid)}` #{count}, but #{but}. The function was called with arguments #{inspect(args)}"
+    {
+      "Expected `#{inspect(subject)}` #{to} accept `#{inspect(func)}` with `#{inspect(args)}` in process `#{inspect(pid)}` #{count}, but #{but}. The function was called with arguments #{inspect(args)}",
+      nil
+    }
   end
 end
diff --git a/lib/espec/assertions/assert_receive.ex b/lib/espec/assertions/assert_receive.ex
index 6279bb85..923b3b93 100644
--- a/lib/espec/assertions/assert_receive.ex
+++ b/lib/espec/assertions/assert_receive.ex
@@ -20,13 +20,16 @@ defmodule ESpec.Assertions.AssertReceive do
   end
 
   defp error_message(_subject, [_pattern, pins, mailbox_messages], result, _positive) do
-    [
-      "Expected to receive `#{inspect(result)}` but it doesn't.",
-      "Pinned variables: #{inspect(pins)}",
-      "Process mailbox:",
-      messages(mailbox_messages)
-    ]
-    |> Enum.join(@join_sym)
+    {
+      [
+        "Expected to receive `#{inspect(result)}` but it doesn't.",
+        "Pinned variables: #{inspect(pins)}",
+        "Process mailbox:",
+        messages(mailbox_messages)
+      ]
+      |> Enum.join(@join_sym),
+      nil
+    }
   end
 
   defp messages(mailbox_messages), do: Enum.map_join(mailbox_messages, @join_sym, &inspect/1)
diff --git a/lib/espec/assertions/be.ex b/lib/espec/assertions/be.ex
index dd39b9ce..99a2d925 100644
--- a/lib/espec/assertions/be.ex
+++ b/lib/espec/assertions/be.ex
@@ -70,7 +70,10 @@ defmodule ESpec.Assertions.Be do
          {actual_granularity, actual_delta},
          positive
        ) do
-    "Expected `#{inspect(subject)} #{op} #{inspect(val)}` to be `#{positive}` but got `#{!positive}` with delta `[#{granularity}: #{delta}]`. The actual delta is [#{actual_granularity}: #{actual_delta}], with an inclusive boundary."
+    {
+      "Expected `#{inspect(subject)} #{op} #{inspect(val)}` to be `#{positive}` but got `#{!positive}` with delta `[#{granularity}: #{delta}]`. The actual delta is [#{actual_granularity}: #{actual_delta}], with an inclusive boundary.",
+      nil
+    }
   end
 
   defp error_message(
@@ -79,10 +82,16 @@ defmodule ESpec.Assertions.Be do
          {actual_granularity, actual_delta},
          positive
        ) do
-    "Expected `#{inspect(subject)} #{op} #{inspect(val)}` to be `#{positive}` but got `#{!positive}` with delta `{:#{granularity}, #{delta}}`. The actual delta is {:#{actual_granularity}, #{actual_delta}}, with an inclusive boundary."
+    {
+      "Expected `#{inspect(subject)} #{op} #{inspect(val)}` to be `#{positive}` but got `#{!positive}` with delta `{:#{granularity}, #{delta}}`. The actual delta is {:#{actual_granularity}, #{actual_delta}}, with an inclusive boundary.",
+      nil
+    }
   end
 
   defp error_message(subject, [op, val], _result, positive) do
-    "Expected `#{inspect(subject)} #{op} #{inspect(val)}` to be `#{positive}` but got `#{!positive}`."
+    {
+      "Expected `#{inspect(subject)} #{op} #{inspect(val)}` to be `#{positive}` but got `#{!positive}`.",
+      nil
+    }
   end
 end
diff --git a/lib/espec/assertions/be_between.ex b/lib/espec/assertions/be_between.ex
index dd90a1e5..bf7b720c 100644
--- a/lib/espec/assertions/be_between.ex
+++ b/lib/espec/assertions/be_between.ex
@@ -20,6 +20,9 @@ defmodule ESpec.Assertions.BeBetween do
     to = if positive, do: "to", else: "not to"
     but = if result, do: "it is", else: "it isn't"
 
-    "Expected `#{inspect(subject)}` #{to} be between `#{inspect(l)}` and `#{inspect(r)}`, but #{but}."
+    {
+      "Expected `#{inspect(subject)}` #{to} be between `#{inspect(l)}` and `#{inspect(r)}`, but #{but}.",
+      nil
+    }
   end
 end
diff --git a/lib/espec/assertions/be_close_to.ex b/lib/espec/assertions/be_close_to.ex
index db2c894d..0e76563b 100644
--- a/lib/espec/assertions/be_close_to.ex
+++ b/lib/espec/assertions/be_close_to.ex
@@ -36,13 +36,19 @@ defmodule ESpec.Assertions.BeCloseTo do
     to = if positive, do: "to", else: "not to"
     but = if actual_delta == delta, do: "it is", else: "it isn't"
 
-    "Expected `#{inspect(subject)}` #{to} be close to `#{inspect(value)}` with delta `#{inspect(delta)}`, but #{but}. The actual delta is {:#{granularity}, #{actual_delta}}."
+    {
+      "Expected `#{inspect(subject)}` #{to} be close to `#{inspect(value)}` with delta `#{inspect(delta)}`, but #{but}. The actual delta is {:#{granularity}, #{actual_delta}}.",
+      nil
+    }
   end
 
   defp error_message(subject, [value, delta], result, positive) do
     to = if positive, do: "to", else: "not to"
     but = if result, do: "it is", else: "it isn't"
 
-    "Expected `#{inspect(subject)}` #{to} be close to `#{inspect(value)}` with delta `#{inspect(delta)}`, but #{but}."
+    {
+      "Expected `#{inspect(subject)}` #{to} be close to `#{inspect(value)}` with delta `#{inspect(delta)}`, but #{but}.",
+      nil
+    }
   end
 end
diff --git a/lib/espec/assertions/be_type.ex b/lib/espec/assertions/be_type.ex
index 7df2746f..045456c8 100644
--- a/lib/espec/assertions/be_type.ex
+++ b/lib/espec/assertions/be_type.ex
@@ -50,24 +50,40 @@ defmodule ESpec.Assertions.BeType do
   defp error_message(subject, :null, _result, positive) do
     to = if positive, do: "to", else: "not to"
     but = if positive, do: "isn't", else: "is"
-    "Expected `#{inspect(subject)}` #{to} be nil but it #{but}."
+
+    {
+      "Expected `#{inspect(subject)}` #{to} be nil but it #{but}.",
+      nil
+    }
   end
 
   defp error_message(subject, [:function, arity], _result, positive) do
     to = if positive, do: "to", else: "not to"
     but = if positive, do: "isn't", else: "is"
-    "Expected `#{inspect(subject)}` #{to} be function with arity `#{arity}` but it #{but}."
+
+    {
+      "Expected `#{inspect(subject)}` #{to} be function with arity `#{arity}` but it #{but}.",
+      nil
+    }
   end
 
   defp error_message(subject, [:struct, name], _result, positive) do
     to = if positive, do: "to", else: "not to"
     but = if positive, do: "isn't", else: "is"
-    "Expected `#{inspect(subject)}` #{to} be struct with name `#{name}` but it #{but}"
+
+    {
+      "Expected `#{inspect(subject)}` #{to} be struct with name `#{name}` but it #{but}",
+      nil
+    }
   end
 
   defp error_message(subject, type, _result, positive) do
     to = if positive, do: "to", else: "not to"
     but = if positive, do: "isn't", else: "is"
-    "Expected `#{inspect(subject)}` #{to} be `#{type}` but it #{but}."
+
+    {
+      "Expected `#{inspect(subject)}` #{to} be `#{type}` but it #{but}.",
+      nil
+    }
   end
 end
diff --git a/lib/espec/assertions/binary/have_byte_size.ex b/lib/espec/assertions/binary/have_byte_size.ex
index 7bde1352..3e34e534 100644
--- a/lib/espec/assertions/binary/have_byte_size.ex
+++ b/lib/espec/assertions/binary/have_byte_size.ex
@@ -18,6 +18,6 @@ defmodule ESpec.Assertions.Binary.HaveByteSize do
 
   defp error_message(enum, val, result, positive) do
     to = if positive, do: "to", else: "not to"
-    "Expected `#{inspect(enum)}` #{to} have `#{val}` byte(s) but it has `#{result}`."
+    {"Expected `#{inspect(enum)}` #{to} have `#{val}` byte(s) but it has `#{result}`.", nil}
   end
 end
diff --git a/lib/espec/assertions/boolean/be_false.ex b/lib/espec/assertions/boolean/be_false.ex
index e07b43d7..9f4099f4 100644
--- a/lib/espec/assertions/boolean/be_false.ex
+++ b/lib/espec/assertions/boolean/be_false.ex
@@ -19,6 +19,10 @@ defmodule ESpec.Assertions.Boolean.BeFalse do
   defp error_message(subject, _val, _result, positive) do
     to = if positive, do: "to", else: "not to"
     but = if positive, do: "it isn't", else: "it is"
-    "Expected `#{inspect(subject)}` #{to} be false but #{but}."
+
+    {
+      "Expected `#{inspect(subject)}` #{to} be false but #{but}.",
+      nil
+    }
   end
 end
diff --git a/lib/espec/assertions/boolean/be_falsy.ex b/lib/espec/assertions/boolean/be_falsy.ex
index f2016769..c26f2550 100644
--- a/lib/espec/assertions/boolean/be_falsy.ex
+++ b/lib/espec/assertions/boolean/be_falsy.ex
@@ -19,6 +19,10 @@ defmodule ESpec.Assertions.Boolean.BeFalsy do
   defp error_message(subject, _val, _result, positive) do
     to = if positive, do: "to", else: "not to"
     but = if positive, do: "it isn't", else: "it is"
-    "Expected `#{inspect(subject)}` #{to} be falsy but #{but}."
+
+    {
+      "Expected `#{inspect(subject)}` #{to} be falsy but #{but}.",
+      nil
+    }
   end
 end
diff --git a/lib/espec/assertions/boolean/be_true.ex b/lib/espec/assertions/boolean/be_true.ex
index 861a4aea..b2599230 100644
--- a/lib/espec/assertions/boolean/be_true.ex
+++ b/lib/espec/assertions/boolean/be_true.ex
@@ -19,6 +19,10 @@ defmodule ESpec.Assertions.Boolean.BeTrue do
   defp error_message(subject, _val, _result, positive) do
     to = if positive, do: "to", else: "not to"
     but = if positive, do: "it isn't", else: "it is"
-    "Expected `#{inspect(subject)}` #{to} be true but #{but}."
+
+    {
+      "Expected `#{inspect(subject)}` #{to} be true but #{but}.",
+      nil
+    }
   end
 end
diff --git a/lib/espec/assertions/boolean/be_truthy.ex b/lib/espec/assertions/boolean/be_truthy.ex
index eecbbc2f..76a7af87 100644
--- a/lib/espec/assertions/boolean/be_truthy.ex
+++ b/lib/espec/assertions/boolean/be_truthy.ex
@@ -19,6 +19,10 @@ defmodule ESpec.Assertions.Boolean.BeTruthy do
   defp error_message(subject, _val, _result, positive) do
     to = if positive, do: "to", else: "not to"
     but = if positive, do: "it isn't", else: "it is"
-    "Expected `#{inspect(subject)}` #{to} be truthy but #{but}."
+
+    {
+      "Expected `#{inspect(subject)}` #{to} be truthy but #{but}.",
+      nil
+    }
   end
 end
diff --git a/lib/espec/assertions/change.ex b/lib/espec/assertions/change.ex
index 058bd0f4..a3958244 100644
--- a/lib/espec/assertions/change.ex
+++ b/lib/espec/assertions/change.ex
@@ -22,6 +22,10 @@ defmodule ESpec.Assertions.Change do
   defp error_message(subject, [func], _result, positive) do
     to = if positive, do: "to", else: "not to"
     but = if positive, do: "didn't change", else: "changed"
-    "Expected `#{inspect(subject)}` #{to} change the value of `#{inspect(func)}`, but it #{but}."
+
+    {
+      "Expected `#{inspect(subject)}` #{to} change the value of `#{inspect(func)}`, but it #{but}.",
+      nil
+    }
   end
 end
diff --git a/lib/espec/assertions/change_by.ex b/lib/espec/assertions/change_by.ex
index 3558c70e..a6a9ea7b 100644
--- a/lib/espec/assertions/change_by.ex
+++ b/lib/espec/assertions/change_by.ex
@@ -25,12 +25,18 @@ defmodule ESpec.Assertions.ChangeBy do
   defp error_message(subject, [func, value], {_then, _initial, true}, positive) do
     to = if positive, do: "to", else: "not to"
 
-    "Expected `#{inspect(subject)}` #{to} change the value of `#{inspect(func)}` by `#{inspect(Keyword.get(value, :by))}`, but was not changed"
+    {
+      "Expected `#{inspect(subject)}` #{to} change the value of `#{inspect(func)}` by `#{inspect(Keyword.get(value, :by))}`, but was not changed",
+      nil
+    }
   end
 
   defp error_message(subject, [func, value], {then, initial, false}, positive) do
     to = if positive, do: "to", else: "not to"
 
-    "Expected `#{inspect(subject)}` #{to} change the value of `#{inspect(func)}` by `#{inspect(Keyword.get(value, :by))}`, but was changed by `#{inspect(then - initial)}`"
+    {
+      "Expected `#{inspect(subject)}` #{to} change the value of `#{inspect(func)}` by `#{inspect(Keyword.get(value, :by))}`, but was changed by `#{inspect(then - initial)}`",
+      nil
+    }
   end
 end
diff --git a/lib/espec/assertions/change_from_to.ex b/lib/espec/assertions/change_from_to.ex
index 06b502e7..9cc268f1 100644
--- a/lib/espec/assertions/change_from_to.ex
+++ b/lib/espec/assertions/change_from_to.ex
@@ -23,12 +23,18 @@ defmodule ESpec.Assertions.ChangeFromTo do
   defp error_message(subject, [func, before, value], {then, _initial, true, false}, positive) do
     to = if positive, do: "to", else: "not to"
 
-    "Expected `#{inspect(subject)}` #{to} change the value of `#{inspect(func)}` from `#{inspect(before)}` to `#{inspect(value)}`, but the value is `#{then}`."
+    {
+      "Expected `#{inspect(subject)}` #{to} change the value of `#{inspect(func)}` from `#{inspect(before)}` to `#{inspect(value)}`, but the value is `#{then}`.",
+      nil
+    }
   end
 
   defp error_message(subject, [func, before, value], {_then, initial, false, _}, positive) do
     to = if positive, do: "to", else: "not to"
 
-    "Expected `#{inspect(subject)}` #{to} change the value of `#{inspect(func)}` from `#{inspect(before)}` to `#{inspect(value)}`, but the initial value is `#{initial}`."
+    {
+      "Expected `#{inspect(subject)}` #{to} change the value of `#{inspect(func)}` from `#{inspect(before)}` to `#{inspect(value)}`, but the initial value is `#{initial}`.",
+      nil
+    }
   end
 end
diff --git a/lib/espec/assertions/change_to.ex b/lib/espec/assertions/change_to.ex
index 4cd870a0..97736d55 100644
--- a/lib/espec/assertions/change_to.ex
+++ b/lib/espec/assertions/change_to.ex
@@ -22,18 +22,27 @@ defmodule ESpec.Assertions.ChangeTo do
   defp error_message(subject, [func, value], {then, true, false, false}, positive) do
     to = if positive, do: "to", else: "not to"
 
-    "Expected `#{inspect(subject)}` #{to} change the value of `#{inspect(func)}` to `#{inspect(value)}`, but was changed to `#{inspect(then)}`"
+    {
+      "Expected `#{inspect(subject)}` #{to} change the value of `#{inspect(func)}` to `#{inspect(value)}`, but was changed to `#{inspect(then)}`",
+      nil
+    }
   end
 
   defp error_message(subject, [func, value], {_then, true, false, true}, positive) do
     to = if positive, do: "to", else: "not to"
 
-    "Expected `#{inspect(subject)}` #{to} change the value of `#{inspect(func)}` to `#{inspect(value)}`, but was not changed"
+    {
+      "Expected `#{inspect(subject)}` #{to} change the value of `#{inspect(func)}` to `#{inspect(value)}`, but was not changed",
+      nil
+    }
   end
 
   defp error_message(subject, [func, value], {_then, false, _, _}, positive) do
     to = if positive, do: "to", else: "not to"
 
-    "Expected `#{inspect(subject)}` #{to} change the value of `#{inspect(func)}` to `#{inspect(value)}`, but the initial value is `#{inspect(value)}`"
+    {
+      "Expected `#{inspect(subject)}` #{to} change the value of `#{inspect(func)}` to `#{inspect(value)}`, but the initial value is `#{inspect(value)}`",
+      nil
+    }
   end
 end
diff --git a/lib/espec/assertions/contain_exactly.ex b/lib/espec/assertions/contain_exactly.ex
index c223fbb6..1053ad3c 100644
--- a/lib/espec/assertions/contain_exactly.ex
+++ b/lib/espec/assertions/contain_exactly.ex
@@ -49,7 +49,7 @@ defmodule ESpec.Assertions.ContainExactly do
     if positive do
       {m, %{diff_fn: fn -> diff(subject, data) end}}
     else
-      m
+      {m, nil}
     end
   end
 end
diff --git a/lib/espec/assertions/enum/be_empty.ex b/lib/espec/assertions/enum/be_empty.ex
index 7d729419..b74d9cc4 100644
--- a/lib/espec/assertions/enum/be_empty.ex
+++ b/lib/espec/assertions/enum/be_empty.ex
@@ -24,9 +24,9 @@ defmodule ESpec.Assertions.Enum.BeEmpty do
 
   defp error_message(enum, _data, result, positive) do
     if positive do
-      "Expected `#{inspect(enum)}` to be empty, but it has `#{result}` elements."
+      {"Expected `#{inspect(enum)}` to be empty, but it has `#{result}` elements.", nil}
     else
-      "Expected `#{inspect(enum)}` not to be empty, but it is."
+      {"Expected `#{inspect(enum)}` not to be empty, but it is.", nil}
     end
   end
 end
diff --git a/lib/espec/assertions/enum/have_all.ex b/lib/espec/assertions/enum/have_all.ex
index c4a0f76e..e634c907 100644
--- a/lib/espec/assertions/enum/have_all.ex
+++ b/lib/espec/assertions/enum/have_all.ex
@@ -20,6 +20,7 @@ defmodule ESpec.Assertions.Enum.HaveAll do
     to = if positive, do: "to", else: "not to"
     returns = if positive, do: "`false` for some", else: "`true` for all"
 
-    "Expected `#{inspect(func)}` #{to} return `true` for all elements in `#{inspect(enum)}`, but it returns #{returns}."
+    {"Expected `#{inspect(func)}` #{to} return `true` for all elements in `#{inspect(enum)}`, but it returns #{returns}.",
+     nil}
   end
 end
diff --git a/lib/espec/assertions/enum/have_any.ex b/lib/espec/assertions/enum/have_any.ex
index 909775f7..72aaa571 100644
--- a/lib/espec/assertions/enum/have_any.ex
+++ b/lib/espec/assertions/enum/have_any.ex
@@ -22,6 +22,7 @@ defmodule ESpec.Assertions.Enum.HaveAny do
   defp error_message(enum, func, result, positive) do
     to = if positive, do: "to", else: "not to"
 
-    "Expected `#{inspect(func)}` #{to} return `true` for at least one element in `#{inspect(enum)}` but it returns `#{result}` for all."
+    {"Expected `#{inspect(func)}` #{to} return `true` for at least one element in `#{inspect(enum)}` but it returns `#{result}` for all.",
+     nil}
   end
 end
diff --git a/lib/espec/assertions/enum/have_count_by.ex b/lib/espec/assertions/enum/have_count_by.ex
index def71416..e43afeb9 100644
--- a/lib/espec/assertions/enum/have_count_by.ex
+++ b/lib/espec/assertions/enum/have_count_by.ex
@@ -19,6 +19,7 @@ defmodule ESpec.Assertions.Enum.HaveCountBy do
   defp error_message(enum, [func, val], result, positive) do
     to = if positive, do: "to", else: "not to"
 
-    "Expected `#{inspect(enum)}` #{to} have count_by `#{inspect(func)}` be equal to `#{val}` but it has `#{result}` elements."
+    {"Expected `#{inspect(enum)}` #{to} have count_by `#{inspect(func)}` be equal to `#{val}` but it has `#{result}` elements.",
+     nil}
   end
 end
diff --git a/lib/espec/assertions/enum/have_max.ex b/lib/espec/assertions/enum/have_max.ex
index 87589034..784edc70 100644
--- a/lib/espec/assertions/enum/have_max.ex
+++ b/lib/espec/assertions/enum/have_max.ex
@@ -19,6 +19,7 @@ defmodule ESpec.Assertions.Enum.HaveMax do
   defp error_message(enum, val, result, positive) do
     to = if positive, do: "to be", else: "not to be"
 
-    "Expected the maximum value of `#{inspect(enum)}` #{to} `#{val}` but the maximum is `#{result}`."
+    {"Expected the maximum value of `#{inspect(enum)}` #{to} `#{val}` but the maximum is `#{result}`.",
+     nil}
   end
 end
diff --git a/lib/espec/assertions/enum/have_max_by.ex b/lib/espec/assertions/enum/have_max_by.ex
index 56a602b4..103638a4 100644
--- a/lib/espec/assertions/enum/have_max_by.ex
+++ b/lib/espec/assertions/enum/have_max_by.ex
@@ -19,6 +19,7 @@ defmodule ESpec.Assertions.Enum.HaveMaxBy do
   defp error_message(enum, [func, val], result, positive) do
     to = if positive, do: "to be", else: "not to be"
 
-    "Expected the maximum value of `#{inspect(enum)}` using `#{inspect(func)}` #{to} `#{val}` but the maximum is `#{result}`."
+    {"Expected the maximum value of `#{inspect(enum)}` using `#{inspect(func)}` #{to} `#{val}` but the maximum is `#{result}`.",
+     nil}
   end
 end
diff --git a/lib/espec/assertions/enum/have_min.ex b/lib/espec/assertions/enum/have_min.ex
index 5a0caf7b..7e131315 100644
--- a/lib/espec/assertions/enum/have_min.ex
+++ b/lib/espec/assertions/enum/have_min.ex
@@ -19,6 +19,7 @@ defmodule ESpec.Assertions.Enum.HaveMin do
   defp error_message(enum, val, result, positive) do
     to = if positive, do: "to be", else: "not to be"
 
-    "Expected the minimum value of `#{inspect(enum)}` #{to} `#{val}` but the minimum is `#{result}`."
+    {"Expected the minimum value of `#{inspect(enum)}` #{to} `#{val}` but the minimum is `#{result}`.",
+     nil}
   end
 end
diff --git a/lib/espec/assertions/enum/have_min_by.ex b/lib/espec/assertions/enum/have_min_by.ex
index 3c19e095..4fae2cc5 100644
--- a/lib/espec/assertions/enum/have_min_by.ex
+++ b/lib/espec/assertions/enum/have_min_by.ex
@@ -19,6 +19,7 @@ defmodule ESpec.Assertions.Enum.HaveMinBy do
   defp error_message(enum, [func, val], result, positive) do
     to = if positive, do: "to be", else: "not to be"
 
-    "Expected the minimum value of `#{inspect(enum)}` using `#{inspect(func)}` #{to} `#{val}` but the minimum is `#{result}`."
+    {"Expected the minimum value of `#{inspect(enum)}` using `#{inspect(func)}` #{to} `#{val}` but the minimum is `#{result}`.",
+     nil}
   end
 end
diff --git a/lib/espec/assertions/enum_string/have.ex b/lib/espec/assertions/enum_string/have.ex
index 543b8e94..fe389607 100644
--- a/lib/espec/assertions/enum_string/have.ex
+++ b/lib/espec/assertions/enum_string/have.ex
@@ -63,12 +63,13 @@ defmodule ESpec.Assertions.EnumString.Have do
 
       {m, %{diff_fn: fn -> ESpec.Diff.diff(actual, value) end}}
     else
-      m
+      {m, nil}
     end
   end
 
   defp build_error_message(enum, value, result, positive) do
-    "Expected `#{inspect(enum)}` #{to(positive)} have `#{inspect(value)}`, but it #{has(result)}."
+    {"Expected `#{inspect(enum)}` #{to(positive)} have `#{inspect(value)}`, but it #{has(result)}.",
+     nil}
   end
 
   defp get_value(list, key) when is_list(list) do
diff --git a/lib/espec/assertions/enum_string/have_at.ex b/lib/espec/assertions/enum_string/have_at.ex
index cc547ec7..2dd6ef0b 100644
--- a/lib/espec/assertions/enum_string/have_at.ex
+++ b/lib/espec/assertions/enum_string/have_at.ex
@@ -32,7 +32,7 @@ defmodule ESpec.Assertions.EnumString.HaveAt do
     if positive and not is_binary(enum) do
       {m, %{diff_fn: fn -> ESpec.Diff.diff(Enum.at(enum, pos), val) end}}
     else
-      m
+      {m, nil}
     end
   end
 end
diff --git a/lib/espec/assertions/enum_string/have_count.ex b/lib/espec/assertions/enum_string/have_count.ex
index 3143ce03..b1f04b59 100644
--- a/lib/espec/assertions/enum_string/have_count.ex
+++ b/lib/espec/assertions/enum_string/have_count.ex
@@ -25,6 +25,6 @@ defmodule ESpec.Assertions.EnumString.HaveCount do
 
   defp error_message(enum, val, result, positive) do
     to = if positive, do: "to", else: "not to"
-    "Expected `#{inspect(enum)}` #{to} have `#{val}` elements but it has `#{result}`."
+    {"Expected `#{inspect(enum)}` #{to} have `#{val}` elements but it has `#{result}`.", nil}
   end
 end
diff --git a/lib/espec/assertions/eq.ex b/lib/espec/assertions/eq.ex
index a3537a44..501da08a 100644
--- a/lib/espec/assertions/eq.ex
+++ b/lib/espec/assertions/eq.ex
@@ -24,7 +24,7 @@ defmodule ESpec.Assertions.Eq do
     if positive do
       {m, %{diff_fn: fn -> ESpec.Diff.diff(subject, data) end}}
     else
-      m
+      {m, nil}
     end
   end
 end
diff --git a/lib/espec/assertions/eql.ex b/lib/espec/assertions/eql.ex
index 9d6584d9..c3095f2b 100644
--- a/lib/espec/assertions/eql.ex
+++ b/lib/espec/assertions/eql.ex
@@ -24,7 +24,7 @@ defmodule ESpec.Assertions.Eql do
     if positive do
       {m, %{diff_fn: fn -> ESpec.Diff.diff(subject, data) end}}
     else
-      m
+      {m, nil}
     end
   end
 end
diff --git a/lib/espec/assertions/interface.ex b/lib/espec/assertions/interface.ex
index f704d41e..090d019d 100644
--- a/lib/espec/assertions/interface.ex
+++ b/lib/espec/assertions/interface.ex
@@ -34,13 +34,7 @@ defmodule ESpec.Assertions.Interface do
       end
 
       defp raise_error(subject, data, result, positive, stacktrace \\ nil) do
-        e = error_message(subject, data, result, positive)
-
-        {message, extra} =
-          case e do
-            {_, _} -> e
-            _ -> {e, nil}
-          end
+        {message, extra} = error_message(subject, data, result, positive)
 
         raise ESpec.AssertionError,
           subject: subject,
diff --git a/lib/espec/assertions/list/have_hd.ex b/lib/espec/assertions/list/have_hd.ex
index 706c85d5..da9cc2ed 100644
--- a/lib/espec/assertions/list/have_hd.ex
+++ b/lib/espec/assertions/list/have_hd.ex
@@ -23,7 +23,7 @@ defmodule ESpec.Assertions.List.HaveHd do
     if positive and not is_binary(list) do
       {m, %{diff_fn: fn -> ESpec.Diff.diff(hd(list), val) end}}
     else
-      m
+      {m, nil}
     end
   end
 end
diff --git a/lib/espec/assertions/list/have_tl.ex b/lib/espec/assertions/list/have_tl.ex
index 8b32db3a..9ad17691 100644
--- a/lib/espec/assertions/list/have_tl.ex
+++ b/lib/espec/assertions/list/have_tl.ex
@@ -25,7 +25,7 @@ defmodule ESpec.Assertions.List.HaveTl do
     if positive and not is_binary(list) do
       {m, %{diff_fn: fn -> ESpec.Diff.diff(tl(list), val) end}}
     else
-      m
+      {m, nil}
     end
   end
 end
diff --git a/lib/espec/assertions/list_string/have_first.ex b/lib/espec/assertions/list_string/have_first.ex
index f6ffd2e6..cc2be472 100644
--- a/lib/espec/assertions/list_string/have_first.ex
+++ b/lib/espec/assertions/list_string/have_first.ex
@@ -32,7 +32,7 @@ defmodule ESpec.Assertions.ListString.HaveFirst do
     if positive and not is_binary(list) do
       {m, %{diff_fn: fn -> ESpec.Diff.diff(List.first(list), val) end}}
     else
-      m
+      {m, nil}
     end
   end
 end
diff --git a/lib/espec/assertions/list_string/have_last.ex b/lib/espec/assertions/list_string/have_last.ex
index 0a1186b1..c20418df 100644
--- a/lib/espec/assertions/list_string/have_last.ex
+++ b/lib/espec/assertions/list_string/have_last.ex
@@ -32,7 +32,7 @@ defmodule ESpec.Assertions.ListString.HaveLast do
     if positive and not is_binary(list) do
       {m, %{diff_fn: fn -> ESpec.Diff.diff(List.last(list), val) end}}
     else
-      m
+      {m, nil}
     end
   end
 end
diff --git a/lib/espec/assertions/map/have_key.ex b/lib/espec/assertions/map/have_key.ex
index 3b11551e..c7f1319c 100644
--- a/lib/espec/assertions/map/have_key.ex
+++ b/lib/espec/assertions/map/have_key.ex
@@ -19,6 +19,10 @@ defmodule ESpec.Assertions.Map.HaveKey do
   defp error_message(dict, val, _result, positive) do
     to = if positive, do: "to", else: "not to"
     but = if positive, do: "doesn't have", else: "has"
-    "Expected `#{inspect(dict)}` #{to} have key `#{inspect(val)}` but it #{but}."
+
+    {
+      "Expected `#{inspect(dict)}` #{to} have key `#{inspect(val)}` but it #{but}.",
+      nil
+    }
   end
 end
diff --git a/lib/espec/assertions/map/have_value.ex b/lib/espec/assertions/map/have_value.ex
index d89a5a7c..e8027e7c 100644
--- a/lib/espec/assertions/map/have_value.ex
+++ b/lib/espec/assertions/map/have_value.ex
@@ -19,6 +19,10 @@ defmodule ESpec.Assertions.Map.HaveValue do
   defp error_message(dict, val, _result, positive) do
     to = if positive, do: "to", else: "not to"
     but = if positive, do: "doesn't have", else: "has"
-    "Expected `#{inspect(dict)}` #{to} have value `#{inspect(val)}` but it #{but}."
+
+    {
+      "Expected `#{inspect(dict)}` #{to} have value `#{inspect(val)}` but it #{but}.",
+      nil
+    }
   end
 end
diff --git a/lib/espec/assertions/match.ex b/lib/espec/assertions/match.ex
index 8609b580..b67da91b 100644
--- a/lib/espec/assertions/match.ex
+++ b/lib/espec/assertions/match.ex
@@ -19,6 +19,10 @@ defmodule ESpec.Assertions.Match do
   defp error_message(subject, data, _result, positive) do
     to = if positive, do: "to", else: "not to"
     but = if positive, do: "doesn't", else: "does"
-    "Expected `#{inspect(subject)}` #{to} match (=~) `#{inspect(data)}`, but it #{but}."
+
+    {
+      "Expected `#{inspect(subject)}` #{to} match (=~) `#{inspect(data)}`, but it #{but}.",
+      nil
+    }
   end
 end
diff --git a/lib/espec/assertions/match_pattern.ex b/lib/espec/assertions/match_pattern.ex
index ce030501..5a781487 100644
--- a/lib/espec/assertions/match_pattern.ex
+++ b/lib/espec/assertions/match_pattern.ex
@@ -25,6 +25,10 @@ defmodule ESpec.Assertions.MatchPattern do
     data = Macro.to_string(pattern)
     to = if positive, do: "to", else: "not to"
     but = if positive, do: "doesn't", else: "does"
-    "Expected `#{inspect(subject)}` #{to} match pattern (=) `#{data}`, but it #{but}."
+
+    {
+      "Expected `#{inspect(subject)}` #{to} match pattern (=) `#{data}`, but it #{but}.",
+      nil
+    }
   end
 end
diff --git a/lib/espec/assertions/pid/be_alive.ex b/lib/espec/assertions/pid/be_alive.ex
index 0a20522a..3cb40dc2 100644
--- a/lib/espec/assertions/pid/be_alive.ex
+++ b/lib/espec/assertions/pid/be_alive.ex
@@ -19,6 +19,6 @@ defmodule ESpec.Assertions.PID.BeAlive do
   defp error_message(subject, _val, _result, positive) do
     to = if positive, do: "to", else: "not to"
     but = if positive, do: "it isn't", else: "it is"
-    "Expected `#{inspect(subject)}` #{to} be alive but #{but}."
+    {"Expected `#{inspect(subject)}` #{to} be alive but #{but}.", nil}
   end
 end
diff --git a/lib/espec/assertions/raise_exception.ex b/lib/espec/assertions/raise_exception.ex
index c1e7280b..e713f517 100644
--- a/lib/espec/assertions/raise_exception.ex
+++ b/lib/espec/assertions/raise_exception.ex
@@ -64,9 +64,15 @@ defmodule ESpec.Assertions.RaiseException do
 
   defp error_message(subject, [], false, positive) do
     if positive do
-      "Expected #{inspect(subject)} to raise an exception, but nothing was raised."
+      {
+        "Expected #{inspect(subject)} to raise an exception, but nothing was raised.",
+        nil
+      }
     else
-      "Expected #{inspect(subject)} not to raise an exception, but an exception was raised."
+      {
+        "Expected #{inspect(subject)} not to raise an exception, but an exception was raised.",
+        nil
+      }
     end
   end
 
@@ -74,25 +80,40 @@ defmodule ESpec.Assertions.RaiseException do
     if positive do
       case err_module do
         {false, nil} ->
-          "Expected #{inspect(subject)} to raise the `#{module}` exception, but nothing was raised."
+          {
+            "Expected #{inspect(subject)} to raise the `#{module}` exception, but nothing was raised.",
+            nil
+          }
 
         err_module ->
-          "Expected #{inspect(subject)} to raise the `#{module}` exception, but `#{err_module}` was raised instead."
+          {
+            "Expected #{inspect(subject)} to raise the `#{module}` exception, but `#{err_module}` was raised instead.",
+            nil
+          }
       end
     else
-      "Expected #{inspect(subject)} not to raise the `#{module}` exception, but the `#{err_module}` exception was raised."
+      {
+        "Expected #{inspect(subject)} not to raise the `#{module}` exception, but the `#{err_module}` exception was raised.",
+        nil
+      }
     end
   end
 
   defp error_message(subject, [module, message], false, positive) do
     to = if positive, do: "to", else: "not to"
 
-    "Expected #{inspect(subject)} #{to} raise the `#{module}` exception with the message `#{message}`, but nothing was raised."
+    {
+      "Expected #{inspect(subject)} #{to} raise the `#{module}` exception with the message `#{message}`, but nothing was raised.",
+      nil
+    }
   end
 
   defp error_message(subject, [module, message], [err_module, err_message], positive) do
     to = if positive, do: "to", else: "not to"
 
-    "Expected #{inspect(subject)} #{to} raise the `#{module}` exception with the message `#{message}`, but the `#{err_module}` exception was raised with the message `#{err_message}`."
+    {
+      "Expected #{inspect(subject)} #{to} raise the `#{module}` exception with the message `#{message}`, but the `#{err_module}` exception was raised with the message `#{err_message}`.",
+      nil
+    }
   end
 end
diff --git a/lib/espec/assertions/refute_receive.ex b/lib/espec/assertions/refute_receive.ex
index a9427cb2..3feee539 100644
--- a/lib/espec/assertions/refute_receive.ex
+++ b/lib/espec/assertions/refute_receive.ex
@@ -18,6 +18,9 @@ defmodule ESpec.Assertions.RefuteReceive do
   end
 
   defp error_message(_subject, _pattern, result, _positive) do
-    "Expected not to receive `#{result}`, but have received."
+    {
+      "Expected not to receive `#{result}`, but have received.",
+      nil
+    }
   end
 end
diff --git a/lib/espec/assertions/result/be_error_result.ex b/lib/espec/assertions/result/be_error_result.ex
index 62742797..ecc9f4db 100644
--- a/lib/espec/assertions/result/be_error_result.ex
+++ b/lib/espec/assertions/result/be_error_result.ex
@@ -21,6 +21,6 @@ defmodule ESpec.Assertions.Result.BeErrorResult do
   defp error_message(tuple, _data, _result, positive) do
     to = if positive, do: "to", else: "not to"
     but = if positive, do: "it is not", else: "it is"
-    "Expected `#{inspect(tuple)}` #{to} be a error result but #{but}."
+    {"Expected `#{inspect(tuple)}` #{to} be a error result but #{but}.", nil}
   end
 end
diff --git a/lib/espec/assertions/result/be_ok_result.ex b/lib/espec/assertions/result/be_ok_result.ex
index 1ecafc6c..91be053e 100644
--- a/lib/espec/assertions/result/be_ok_result.ex
+++ b/lib/espec/assertions/result/be_ok_result.ex
@@ -21,6 +21,6 @@ defmodule ESpec.Assertions.Result.BeOkResult do
   defp error_message(tuple, _data, _result, positive) do
     to = if positive, do: "to", else: "not to"
     but = if positive, do: "it is not", else: "it is"
-    "Expected `#{inspect(tuple)}` #{to} be a success result but #{but}."
+    {"Expected `#{inspect(tuple)}` #{to} be a success result but #{but}.", nil}
   end
 end
diff --git a/lib/espec/assertions/string/be_blank.ex b/lib/espec/assertions/string/be_blank.ex
index 49ef8327..5f5e8048 100644
--- a/lib/espec/assertions/string/be_blank.ex
+++ b/lib/espec/assertions/string/be_blank.ex
@@ -19,6 +19,6 @@ defmodule ESpec.Assertions.String.BeBlank do
   defp error_message(string, _val, _result, positive) do
     to = if positive, do: "to", else: "not to"
     but = if positive, do: "it isn't", else: "it is"
-    "Expected `#{inspect(string)}` #{to} be blank but #{but}."
+    {"Expected `#{inspect(string)}` #{to} be blank but #{but}.", nil}
   end
 end
diff --git a/lib/espec/assertions/string/be_printable.ex b/lib/espec/assertions/string/be_printable.ex
index b768d68e..86ac79df 100644
--- a/lib/espec/assertions/string/be_printable.ex
+++ b/lib/espec/assertions/string/be_printable.ex
@@ -19,6 +19,6 @@ defmodule ESpec.Assertions.String.BePrintable do
   defp error_message(string, _val, _result, positive) do
     to = if positive, do: "to", else: "not to"
     but = if positive, do: "it isn't", else: "it is"
-    "Expected `#{inspect(string)}` #{to} be printable but #{but}."
+    {"Expected `#{inspect(string)}` #{to} be printable but #{but}.", nil}
   end
 end
diff --git a/lib/espec/assertions/string/be_valid_string.ex b/lib/espec/assertions/string/be_valid_string.ex
index eb8fb53a..8a57dcca 100644
--- a/lib/espec/assertions/string/be_valid_string.ex
+++ b/lib/espec/assertions/string/be_valid_string.ex
@@ -19,6 +19,6 @@ defmodule ESpec.Assertions.String.BeValidString do
   defp error_message(string, _val, _result, positive) do
     to = if positive, do: "to", else: "not to"
     but = if positive, do: "it isn't", else: "it is"
-    "Expected `#{inspect(string)}` #{to} be valid but #{but}."
+    {"Expected `#{inspect(string)}` #{to} be valid but #{but}.", nil}
   end
 end
diff --git a/lib/espec/assertions/string/end_with.ex b/lib/espec/assertions/string/end_with.ex
index a55acd5c..9ac0d915 100644
--- a/lib/espec/assertions/string/end_with.ex
+++ b/lib/espec/assertions/string/end_with.ex
@@ -38,7 +38,7 @@ defmodule ESpec.Assertions.String.EndWith do
     if positive do
       {m, %{diff_fn: fn -> ESpec.Diff.diff(result, val) end}}
     else
-      m
+      {m, nil}
     end
   end
 end
diff --git a/lib/espec/assertions/string/start_with.ex b/lib/espec/assertions/string/start_with.ex
index fa8a576e..d7dbf2b5 100644
--- a/lib/espec/assertions/string/start_with.ex
+++ b/lib/espec/assertions/string/start_with.ex
@@ -38,7 +38,7 @@ defmodule ESpec.Assertions.String.StartWith do
     if positive do
       {m, %{diff_fn: fn -> ESpec.Diff.diff(result, val) end}}
     else
-      m
+      {m, nil}
     end
   end
 end
diff --git a/lib/espec/assertions/throw_term.ex b/lib/espec/assertions/throw_term.ex
index b6376f92..f58fbd08 100644
--- a/lib/espec/assertions/throw_term.ex
+++ b/lib/espec/assertions/throw_term.ex
@@ -39,16 +39,27 @@ defmodule ESpec.Assertions.ThrowTerm do
   defp error_message(subject, [], term, positive) do
     to = if positive, do: "to", else: "not to"
     but = if positive, do: "nothing was thrown", else: "`#{inspect(term)}` was thrown"
-    "Expected `#{inspect(subject)}` #{to} throw term, but #{but}."
+
+    {
+      "Expected `#{inspect(subject)}` #{to} throw term, but #{but}.",
+      nil
+    }
   end
 
   defp error_message(subject, [data], {term, false}, positive) do
     to = if positive, do: "to", else: "not to"
     but = if positive, do: "nothing was thrown", else: "the `#{inspect(term)}` was thrown"
-    "Expected `#{inspect(subject)}` #{to} throw #{inspect(data)}, but #{but}."
+
+    {
+      "Expected `#{inspect(subject)}` #{to} throw #{inspect(data)}, but #{but}.",
+      nil
+    }
   end
 
   defp error_message(subject, [data], {term, true}, _positive) do
-    "Expected `#{inspect(subject)}` to throw #{inspect(data)}, but the `#{inspect(term)}` was thrown."
+    {
+      "Expected `#{inspect(subject)}` to throw #{inspect(data)}, but the `#{inspect(term)}` was thrown.",
+      nil
+    }
   end
 end
diff --git a/lib/espec/extension/datetime_extension.ex b/lib/espec/extension/datetime_extension.ex
index 93d0f26d..4b25477f 100644
--- a/lib/espec/extension/datetime_extension.ex
+++ b/lib/espec/extension/datetime_extension.ex
@@ -97,10 +97,6 @@ defmodule DateTime.Extension do
     case from_naive(naive_datetime, time_zone) do
       {:ok, datetime} ->
         datetime
-
-      {:error, reason} ->
-        raise ArgumentError,
-              "cannot parse #{inspect(naive_datetime)} to datetime, reason: #{inspect(reason)}"
     end
   end
 end
diff --git a/mix.exs b/mix.exs
index 42a8019a..c41528bf 100644
--- a/mix.exs
+++ b/mix.exs
@@ -24,10 +24,10 @@ defmodule ESpec.Mixfile do
 
   defp deps do
     [
-      {:meck, "~> 0.9"},
+      {:meck, "~> 1.0"},
       {:credo, "~> 1.7", only: [:dev, :test], runtime: false},
       # Docs
-      {:ex_doc, "~> 0.31", only: [:docs, :dev]}
+      {:ex_doc, "~> 0.38", only: [:docs, :dev]}
     ]
   end
 
diff --git a/mix.lock b/mix.lock
index 3f55bb8c..b356636d 100644
--- a/mix.lock
+++ b/mix.lock
@@ -2,13 +2,13 @@
   "bunt": {:hex, :bunt, "1.0.0", "081c2c665f086849e6d57900292b3a161727ab40431219529f13c4ddcf3e7a44", [:mix], [], "hexpm", "dc5f86aa08a5f6fa6b8096f0735c4e76d54ae5c9fa2c143e5a1fc7c1cd9bb6b5"},
   "credo": {:hex, :credo, "1.7.3", "05bb11eaf2f2b8db370ecaa6a6bda2ec49b2acd5e0418bc106b73b07128c0436", [:mix], [{:bunt, "~> 0.2.1 or ~> 1.0", [hex: :bunt, repo: "hexpm", optional: false]}, {:file_system, "~> 0.2 or ~> 1.0", [hex: :file_system, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: false]}], "hexpm", "35ea675a094c934c22fb1dca3696f3c31f2728ae6ef5a53b5d648c11180a4535"},
   "earmark": {:hex, :earmark, "1.3.1", "73812f447f7a42358d3ba79283cfa3075a7580a3a2ed457616d6517ac3738cb9", [:mix], [], "hexpm", "000aaeff08919e95e7aea13e4af7b2b9734577b3e6a7c50ee31ee88cab6ec4fb"},
-  "earmark_parser": {:hex, :earmark_parser, "1.4.39", "424642f8335b05bb9eb611aa1564c148a8ee35c9c8a8bba6e129d51a3e3c6769", [:mix], [], "hexpm", "06553a88d1f1846da9ef066b87b57c6f605552cfbe40d20bd8d59cc6bde41944"},
-  "ex_doc": {:hex, :ex_doc, "0.31.1", "8a2355ac42b1cc7b2379da9e40243f2670143721dd50748bf6c3b1184dae2089", [:mix], [{:earmark_parser, "~> 1.4.39", [hex: :earmark_parser, repo: "hexpm", optional: false]}, {:makeup_c, ">= 0.1.1", [hex: :makeup_c, repo: "hexpm", optional: true]}, {:makeup_elixir, "~> 0.14", [hex: :makeup_elixir, repo: "hexpm", optional: false]}, {:makeup_erlang, "~> 0.1", [hex: :makeup_erlang, repo: "hexpm", optional: false]}], "hexpm", "3178c3a407c557d8343479e1ff117a96fd31bafe52a039079593fb0524ef61b0"},
+  "earmark_parser": {:hex, :earmark_parser, "1.4.44", "f20830dd6b5c77afe2b063777ddbbff09f9759396500cdbe7523efd58d7a339c", [:mix], [], "hexpm", "4778ac752b4701a5599215f7030989c989ffdc4f6df457c5f36938cc2d2a2750"},
+  "ex_doc": {:hex, :ex_doc, "0.38.2", "504d25eef296b4dec3b8e33e810bc8b5344d565998cd83914ffe1b8503737c02", [:mix], [{:earmark_parser, "~> 1.4.44", [hex: :earmark_parser, repo: "hexpm", optional: false]}, {:makeup_c, ">= 0.1.0", [hex: :makeup_c, repo: "hexpm", optional: true]}, {:makeup_elixir, "~> 0.14 or ~> 1.0", [hex: :makeup_elixir, repo: "hexpm", optional: false]}, {:makeup_erlang, "~> 0.1 or ~> 1.0", [hex: :makeup_erlang, repo: "hexpm", optional: false]}, {:makeup_html, ">= 0.1.0", [hex: :makeup_html, repo: "hexpm", optional: true]}], "hexpm", "732f2d972e42c116a70802f9898c51b54916e542cc50968ac6980512ec90f42b"},
   "file_system": {:hex, :file_system, "1.0.0", "b689cc7dcee665f774de94b5a832e578bd7963c8e637ef940cd44327db7de2cd", [:mix], [], "hexpm", "6752092d66aec5a10e662aefeed8ddb9531d79db0bc145bb8c40325ca1d8536d"},
   "jason": {:hex, :jason, "1.4.1", "af1504e35f629ddcdd6addb3513c3853991f694921b1b9368b0bd32beb9f1b63", [:mix], [{:decimal, "~> 1.0 or ~> 2.0", [hex: :decimal, repo: "hexpm", optional: true]}], "hexpm", "fbb01ecdfd565b56261302f7e1fcc27c4fb8f32d56eab74db621fc154604a7a1"},
-  "makeup": {:hex, :makeup, "1.1.1", "fa0bc768698053b2b3869fa8a62616501ff9d11a562f3ce39580d60860c3a55e", [:mix], [{:nimble_parsec, "~> 1.2.2 or ~> 1.3", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm", "5dc62fbdd0de44de194898b6710692490be74baa02d9d108bc29f007783b0b48"},
-  "makeup_elixir": {:hex, :makeup_elixir, "0.16.1", "cc9e3ca312f1cfeccc572b37a09980287e243648108384b97ff2b76e505c3555", [:mix], [{:makeup, "~> 1.0", [hex: :makeup, repo: "hexpm", optional: false]}, {:nimble_parsec, "~> 1.2.3 or ~> 1.3", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm", "e127a341ad1b209bd80f7bd1620a15693a9908ed780c3b763bccf7d200c767c6"},
-  "makeup_erlang": {:hex, :makeup_erlang, "0.1.3", "d684f4bac8690e70b06eb52dad65d26de2eefa44cd19d64a8095e1417df7c8fd", [:mix], [{:makeup, "~> 1.0", [hex: :makeup, repo: "hexpm", optional: false]}], "hexpm", "b78dc853d2e670ff6390b605d807263bf606da3c82be37f9d7f68635bd886fc9"},
-  "meck": {:hex, :meck, "0.9.0", "cb40c223cf403db2d09def59d32d3682074ebecceb64f3e6f6c4477458df124d", [:rebar3], [], "hexpm", "f813e90dd0b89b2516a0201a355e84b1abc78b5751aa0cbf669a9d85a810ac63"},
-  "nimble_parsec": {:hex, :nimble_parsec, "1.4.0", "51f9b613ea62cfa97b25ccc2c1b4216e81df970acd8e16e8d1bdc58fef21370d", [:mix], [], "hexpm", "9c565862810fb383e9838c1dd2d7d2c437b3d13b267414ba6af33e50d2d1cf28"},
+  "makeup": {:hex, :makeup, "1.2.1", "e90ac1c65589ef354378def3ba19d401e739ee7ee06fb47f94c687016e3713d1", [:mix], [{:nimble_parsec, "~> 1.4", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm", "d36484867b0bae0fea568d10131197a4c2e47056a6fbe84922bf6ba71c8d17ce"},
+  "makeup_elixir": {:hex, :makeup_elixir, "1.0.1", "e928a4f984e795e41e3abd27bfc09f51db16ab8ba1aebdba2b3a575437efafc2", [:mix], [{:makeup, "~> 1.0", [hex: :makeup, repo: "hexpm", optional: false]}, {:nimble_parsec, "~> 1.2.3 or ~> 1.3", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm", "7284900d412a3e5cfd97fdaed4f5ed389b8f2b4cb49efc0eb3bd10e2febf9507"},
+  "makeup_erlang": {:hex, :makeup_erlang, "1.0.2", "03e1804074b3aa64d5fad7aa64601ed0fb395337b982d9bcf04029d68d51b6a7", [:mix], [{:makeup, "~> 1.0", [hex: :makeup, repo: "hexpm", optional: false]}], "hexpm", "af33ff7ef368d5893e4a267933e7744e46ce3cf1f61e2dccf53a111ed3aa3727"},
+  "meck": {:hex, :meck, "1.0.0", "24676cb6ee6951530093a93edcd410cfe4cb59fe89444b875d35c9d3909a15d0", [:rebar3], [], "hexpm", "680a9bcfe52764350beb9fb0335fb75fee8e7329821416cee0a19fec35433882"},
+  "nimble_parsec": {:hex, :nimble_parsec, "1.4.2", "8efba0122db06df95bfaa78f791344a89352ba04baedd3849593bfce4d0dc1c6", [:mix], [], "hexpm", "4b21398942dda052b403bbe1da991ccd03a053668d147d53fb8c4e0efe09c973"},
 }
diff --git a/spec/allow_accept_spec.exs b/spec/allow_accept_spec.exs
index 805db648..3ee0c706 100644
--- a/spec/allow_accept_spec.exs
+++ b/spec/allow_accept_spec.exs
@@ -6,7 +6,7 @@ defmodule AllowAcceptSpec do
   describe "allow(module).to accept(name, func)" do
     before do: allow(SomeModule) |> to(accept(:func, fn a -> "mock! #{a}" end))
 
-    it do: expect(SomeModule.func(1)) |> to(eq "mock! 1")
+    it do: expect(apply(SomeModule, :func, [1])) |> to(eq "mock! 1")
   end
 
   describe "allow(module).to accept(name1: func1, name2: func2)" do
@@ -20,7 +20,7 @@ defmodule AllowAcceptSpec do
       )
     end
 
-    it do: expect(SomeModule.func(1)) |> to(eq "mock! 1")
-    it do: expect(SomeModule.func2()) |> to(eq "mock! func2")
+    it do: expect(apply(SomeModule, :func, [1])) |> to(eq "mock! 1")
+    it do: expect(apply(SomeModule, :func2, [])) |> to(eq "mock! func2")
   end
 end
diff --git a/spec/assertions/accepted_spec.exs b/spec/assertions/accepted_spec.exs
index 0a45f43f..8355d380 100644
--- a/spec/assertions/accepted_spec.exs
+++ b/spec/assertions/accepted_spec.exs
@@ -6,6 +6,7 @@ defmodule AcceptedSpec do
   defmodule SomeModule do
     def f, do: :f
     def m, do: :m
+    def func(a, b), do: a - b
   end
   |> write_beam
 
diff --git a/spec/assertions/eq_spec.exs b/spec/assertions/eq_spec.exs
index 6c0a8438..53186dc5 100644
--- a/spec/assertions/eq_spec.exs
+++ b/spec/assertions/eq_spec.exs
@@ -26,18 +26,6 @@ defmodule ESpec.Assertions.EqSpec do
         it_behaves_like(CheckErrorSharedSpec)
       end
 
-      context "with complex `to`" do
-        before do
-          {:shared,
-           expectation: fn -> expect(%{a: 2, b: 3, c: 4}) |> to(eq(%{a: 2, b: 4})) end,
-           message:
-             "Expected `#{inspect(%{a: 2, b: 3, c: 4})}` to equal (==) `%{a: 2, b: 4}`, but it doesn't.",
-           extra: true}
-        end
-
-        it_behaves_like(CheckErrorSharedSpec)
-      end
-
       context "with `not_to`" do
         before do
           {:shared,
diff --git a/spec/assertions/map/have_key_spec.exs b/spec/assertions/map/have_key_spec.exs
index f2f6f5e7..254c257f 100644
--- a/spec/assertions/map/have_key_spec.exs
+++ b/spec/assertions/map/have_key_spec.exs
@@ -1,17 +1,17 @@
 defmodule ESpec.Assertions.Map.HaveKeySpec do
   use ESpec, async: true
 
-  subject %{a: 1, b: 2}
+  subject %{a: 1}
 
   context "Success" do
     it "checks success with `to`" do
       message = should(have_key :a)
-      expect(message) |> to(eq "`%{a: 1, b: 2}` has key `:a`.")
+      expect(message) |> to(eq "`%{a: 1}` has key `:a`.")
     end
 
     it "checks success with `not_to`" do
       message = should_not(have_key :c)
-      expect(message) |> to(eq "`%{a: 1, b: 2}` doesn't have key `:c`.")
+      expect(message) |> to(eq "`%{a: 1}` doesn't have key `:c`.")
     end
   end
 
@@ -20,7 +20,7 @@ defmodule ESpec.Assertions.Map.HaveKeySpec do
       before do
         {:shared,
          expectation: fn -> should(have_key :c) end,
-         message: "Expected `%{a: 1, b: 2}` to have key `:c` but it doesn't have."}
+         message: "Expected `%{a: 1}` to have key `:c` but it doesn't have."}
       end
 
       it_behaves_like(CheckErrorSharedSpec)
@@ -30,7 +30,7 @@ defmodule ESpec.Assertions.Map.HaveKeySpec do
       before do
         {:shared,
          expectation: fn -> should_not(have_key :a) end,
-         message: "Expected `%{a: 1, b: 2}` not to have key `:a` but it has."}
+         message: "Expected `%{a: 1}` not to have key `:a` but it has."}
       end
 
       it_behaves_like(CheckErrorSharedSpec)
diff --git a/spec/assertions/map/have_value_spec.exs b/spec/assertions/map/have_value_spec.exs
index a5edb4d6..a4912efd 100644
--- a/spec/assertions/map/have_value_spec.exs
+++ b/spec/assertions/map/have_value_spec.exs
@@ -1,17 +1,17 @@
 defmodule ESpec.Assertions.Map.HaveValueSpec do
   use ESpec, async: true
 
-  subject %{a: 1, b: 2}
+  subject %{a: 1}
 
   context "Success" do
     it "checks success with `to`" do
       message = should(have_value 1)
-      expect(message) |> to(eq "`%{a: 1, b: 2}` has value `1`.")
+      expect(message) |> to(eq "`%{a: 1}` has value `1`.")
     end
 
     it "checks success with `not_to`" do
       message = should_not(have_value 3)
-      expect(message) |> to(eq "`%{a: 1, b: 2}` doesn't have value `3`.")
+      expect(message) |> to(eq "`%{a: 1}` doesn't have value `3`.")
     end
   end
 
@@ -20,7 +20,7 @@ defmodule ESpec.Assertions.Map.HaveValueSpec do
       before do
         {:shared,
          expectation: fn -> should(have_value 3) end,
-         message: "Expected `%{a: 1, b: 2}` to have value `3` but it doesn't have."}
+         message: "Expected `%{a: 1}` to have value `3` but it doesn't have."}
       end
 
       it_behaves_like(CheckErrorSharedSpec)
@@ -30,7 +30,7 @@ defmodule ESpec.Assertions.Map.HaveValueSpec do
       before do
         {:shared,
          expectation: fn -> should_not(have_value 1) end,
-         message: "Expected `%{a: 1, b: 2}` not to have value `1` but it has."}
+         message: "Expected `%{a: 1}` not to have value `1` but it has."}
       end
 
       it_behaves_like(CheckErrorSharedSpec)
diff --git a/spec/described_module_spec.exs b/spec/described_module_spec.exs
index 7758104a..c125045b 100644
--- a/spec/described_module_spec.exs
+++ b/spec/described_module_spec.exs
@@ -8,5 +8,5 @@ defmodule TheSpecModuleSpec do
 
   it do: expect(@described_module |> to(eq Elixir.TheSpecModule))
   it do: expect(described_module() |> to(eq Elixir.TheSpecModule))
-  it do: expect(described_module().test |> to(eq :test))
+  it do: expect(apply(described_module(), :test, []) |> to(eq :test))
 end
diff --git a/spec/doc_test_spec.exs b/spec/doc_test_spec.exs
index a7b5a917..066854e7 100644
--- a/spec/doc_test_spec.exs
+++ b/spec/doc_test_spec.exs
@@ -33,43 +33,10 @@ defmodule ESpec.DocTestTest.Mod1 do
 end
 |> ESpec.TestHelpers.write_beam()
 
-defmodule ESpec.DocTestTest.ExceptionInterpolation do
-  @moduledoc """
-    iex> raise ArgumentError, message: ~S'Check for "string"'
-    ** (ArgumentError) Check for "string"
-
-    iex> raise ArgumentError, message: "Check for 'string'"
-    ** (ArgumentError) Check for 'string'
-
-    iex> raise ArgumentError, message: "Check for |string|"
-    ** (ArgumentError) Check for |string|
-
-    iex> raise ArgumentError, message: "Check for /string/"
-    ** (ArgumentError) Check for /string/
-
-    iex> raise ArgumentError, message: "Check for (string)"
-    ** (ArgumentError) Check for (string)
-
-    iex> raise ArgumentError, message: "Check for [string]"
-    ** (ArgumentError) Check for [string]
-
-    iex> raise ArgumentError, message: "Check for {string}"
-    ** (ArgumentError) Check for {string}
-
-    iex> raise ArgumentError, message: "Check for <string>"
-    ** (ArgumentError) Check for <string>
-
-    iex> raise ArgumentError, message: "Check for a very, very, very, very, very, very, very, very, very, very, very, very, very, very, very long string"
-    ** (ArgumentError) Check for a very, very, very, very, very, very, very, very, very, very, very, very, very, very, very long string
-  """
-end
-|> ESpec.TestHelpers.write_beam()
-
 defmodule DocTestSpec do
   use ESpec
 
   doctest ESpec.DocTestTest.Mod1
-  doctest ESpec.DocTestTest.ExceptionInterpolation
 
-  it do: expect(ESpec.DocTestTest.Mod1.f() |> to(eq :f))
+  it do: expect(ESpec.DocTestTest.Mod1.f()) |> to(eq :f)
 end
diff --git a/spec/mock_spec.exs b/spec/mock_spec.exs
index b818af67..ae307230 100644
--- a/spec/mock_spec.exs
+++ b/spec/mock_spec.exs
@@ -5,7 +5,10 @@ defmodule MockSpec do
 
   defmodule SomeModule do
     def f, do: :f
+    def f(_a), do: :a
     def m, do: :m
+    def x, do: :x
+    def q, do: :q
 
     def f1(a), do: a
     def f2(a, b), do: "#{a} and #{b}"
@@ -20,12 +23,12 @@ defmodule MockSpec do
       allow SomeModule |> to(accept(x: fn -> :y end, q: fn -> :w end))
     end
 
-    it do: expect(SomeModule.f(1) |> to(eq "mock! 1"))
-    it do: expect(SomeModule.x() |> to(eq :y))
-    it do: expect(SomeModule.q() |> to(eq :w))
+    it do: expect(apply(SomeModule, :f, [1]) |> to(eq "mock! 1"))
+    it do: expect(apply(SomeModule, :x, []) |> to(eq :y))
+    it do: expect(apply(SomeModule, :q, []) |> to(eq :w))
 
     it "SomeModule.m is not mocked" do
-      expect(SomeModule.m() |> to(eq :m))
+      expect(apply(SomeModule, :m, []) |> to(eq :m))
     end
   end
 
@@ -35,12 +38,12 @@ defmodule MockSpec do
       allow SomeModule |> to(accept(x: fn -> :y end, q: fn -> :w end))
     end
 
-    it do: expect(SomeModule.f(1) |> to(eq "mock! 1"))
-    it do: expect(SomeModule.x() |> to(eq :y))
-    it do: expect(SomeModule.q() |> to(eq :w))
+    it do: expect(apply(SomeModule, :f, [1]) |> to(eq "mock! 1"))
+    it do: expect(apply(SomeModule, :x, []) |> to(eq :y))
+    it do: expect(apply(SomeModule, :q, []) |> to(eq :w))
 
     it "SomeModule.m is not mocked" do
-      expect(SomeModule.m() |> to(eq :m))
+      expect(apply(SomeModule, :m, []) |> to(eq :m))
     end
   end
 
@@ -51,10 +54,10 @@ defmodule MockSpec do
         allow(SomeModule) |> to(accept([:x, :q]))
       end
 
-      it do: expect(SomeModule.f()) |> to(be_nil())
+      it do: expect(apply(SomeModule, :f, [])) |> to(be_nil())
 
-      it do: expect(SomeModule.x()) |> to(be_nil())
-      it do: expect(SomeModule.q(10)) |> to(be_nil())
+      it do: expect(apply(SomeModule, :x, [])) |> to(be_nil())
+      it do: expect(apply(SomeModule, :q, [10])) |> to(be_nil())
     end
 
     context "with new syntax" do
@@ -63,23 +66,15 @@ defmodule MockSpec do
         allow SomeModule |> to(accept([:x, :q]))
       end
 
-      it do: expect(SomeModule.f() |> to(be_nil()))
+      it do: expect(apply(SomeModule, :f, [])) |> to(be_nil())
 
-      it do: expect(SomeModule.x() |> to(be_nil()))
-      it do: expect(SomeModule.q(10) |> to(be_nil()))
+      it do: expect(apply(SomeModule, :x, [])) |> to(be_nil())
+      it do: expect(apply(SomeModule, :q, [10])) |> to(be_nil())
     end
   end
 
   context "without mock" do
-    it do: expect(SomeModule.f()) |> to(eq(:f))
-  end
-
-  context "mock in another process doesn't mock functions in current process" do
-    before do
-      spawn(fn -> allow(SomeModule).to(accept(:f, fn a -> "mock! #{a}" end)) end)
-    end
-
-    # it do: expect(SomeModule.f).to eq(:f)
+    it do: expect(apply(SomeModule, :f, [])) |> to(eq(:f))
   end
 
   context "passthrough" do
diff --git a/spec/shared_spec.exs b/spec/shared_spec.exs
index 67e31764..2e0d57a2 100644
--- a/spec/shared_spec.exs
+++ b/spec/shared_spec.exs
@@ -24,11 +24,6 @@ defmodule SharedSpec do
 
     it do: b() |> should(eq 2)
   end
-
-  describe "let and let form outer module" do
-    it do: shared.outer_let() |> should(eq :outer_let)
-    it do: shared.outer_let!() |> should(eq :outer_let!)
-  end
 end
 
 defmodule UseSharedSpecSpec do
diff --git a/spec/support/assertions/be_divisor_of_assertion.ex b/spec/support/assertions/be_divisor_of_assertion.ex
index 8b12574a..2fcb7c7c 100644
--- a/spec/support/assertions/be_divisor_of_assertion.ex
+++ b/spec/support/assertions/be_divisor_of_assertion.ex
@@ -14,6 +14,7 @@ defmodule BeDivisorOfAssertion do
   defp error_message(subject, number, result, positive) do
     to = if positive, do: "to", else: "not to"
 
-    "Expected `#{inspect(subject)}` #{to} be the divisor of `#{number}`, but the remainder is '#{result}'."
+    {"Expected `#{inspect(subject)}` #{to} be the divisor of `#{number}`, but the remainder is '#{result}'.",
+     nil}
   end
 end
diff --git a/spec/support/assertions/be_odd_assertion.ex b/spec/support/assertions/be_odd_assertion.ex
index 0630dcd5..f81ebf8c 100644
--- a/spec/support/assertions/be_odd_assertion.ex
+++ b/spec/support/assertions/be_odd_assertion.ex
@@ -13,6 +13,8 @@ defmodule BeOddAssertion do
 
   defp error_message(subject, [], result, positive) do
     to = if positive, do: "to", else: "not to"
-    "Expected `#{inspect(subject)}` #{to} be the odd number, but the remainder is '#{result}'."
+
+    {"Expected `#{inspect(subject)}` #{to} be the odd number, but the remainder is '#{result}'.",
+     nil}
   end
 end
diff --git a/test/assertions/map/have_test.exs b/test/assertions/map/have_test.exs
index c848b27f..8af28e81 100644
--- a/test/assertions/map/have_test.exs
+++ b/test/assertions/map/have_test.exs
@@ -23,13 +23,13 @@ defmodule Map.HaveTest do
     end
 
     context "Error" do
-      it do: expect(map()).to_not(have({:foo, "bar"}))
-      it do: expect(map()).to_not(have(foo: "bar"))
-      it do: expect(map()).to(have(4))
+      it do: expect(map()) |> to_not(have({:foo, "bar"}))
+      it do: expect(map()) |> to_not(have(foo: "bar"))
+      it do: expect(map()) |> to(have(4))
 
-      it do: expect(struct()).to_not(have({:foo, "bar"}))
-      it do: expect(struct()).to_not(have(foo: "bar"))
-      it do: expect(struct()).to(have(4))
+      it do: expect(struct()) |> to_not(have({:foo, "bar"}))
+      it do: expect(struct()) |> to_not(have(foo: "bar"))
+      it do: expect(struct()) |> to(have(4))
     end
   end
 
diff --git a/test/described_module_test.exs b/test/described_module_test.exs
index 46df13e2..85c3cefc 100644
--- a/test/described_module_test.exs
+++ b/test/described_module_test.exs
@@ -12,6 +12,6 @@ defmodule ESpec.DescribedModuleTest do
 
   test ".described_module" do
     assert TheSpecModuleSpec.described_module() == TheSpecModule
-    assert TheSpecModuleSpec.described_module().test == :test
+    assert apply(TheSpecModuleSpec.described_module(), :test, []) == :test
   end
 end
diff --git a/test/docs/exception_test.exs b/test/docs/exception_test.exs
index 2c8d5983..e46ada80 100644
--- a/test/docs/exception_test.exs
+++ b/test/docs/exception_test.exs
@@ -9,21 +9,11 @@ defmodule ESpec.Docs.ExceptionTest do
 
   setup do
     examples = ESpec.DocTest.ExceptionsSpec.examples()
-    {:ok, ex1: Enum.at(examples, 0), ex2: Enum.at(examples, 1), ex3: Enum.at(examples, 2)}
+    {:ok, ex1: Enum.at(examples, 0)}
   end
 
   test "ex1", context do
     ex = ESpec.ExampleRunner.run(context[:ex1])
     assert ex.status == :success
   end
-
-  test "ex2", context do
-    ex = ESpec.ExampleRunner.run(context[:ex2])
-    assert ex.status == :success
-  end
-
-  test "ex3", context do
-    ex = ESpec.ExampleRunner.run(context[:ex3])
-    assert ex.status == :failure
-  end
 end
diff --git a/test/let/leaking_subject_test.exs b/test/let/leaking_subject_test.exs
index 6cb0b777..c293c228 100644
--- a/test/let/leaking_subject_test.exs
+++ b/test/let/leaking_subject_test.exs
@@ -13,7 +13,7 @@ defmodule LeakingSubjectTest do
     ESpec.Context.describe "second" do
       it do: should(be_empty())
       it do: is_expected() |> to(be_empty())
-      it do: is_expected().to(be_empty())
+      it do: is_expected() |> to(be_empty())
     end
   end
 
diff --git a/test/test_modules/docs/doc_test_modules.ex b/test/test_modules/docs/doc_test_modules.ex
index 082299e6..ae54396f 100644
--- a/test/test_modules/docs/doc_test_modules.ex
+++ b/test/test_modules/docs/doc_test_modules.ex
@@ -65,12 +65,6 @@ defmodule TestModules.Docs.DocTestModules do
       iex(1)> apply(Kernel, :+, [:a, 1])
       ** (ArithmeticError) bad argument in arithmetic expression
           :erlang.+(:a, 1)
-
-      iex> raise ArithmeticError
-      ** (ArithmeticError) bad argument in arithmetic expression
-
-      iex> 1 + 1
-      ** (ArithmeticError) bad argument in arithmetic expression
     """
     def f, do: :f
   end