diff --git a/README.md b/README.md
index 076879e..350e506 100644
--- a/README.md
+++ b/README.md
@@ -87,6 +87,25 @@ To explore the full capabilities, including the property inspector and real-time
 uv run examples/demo.py
 ```
 
+## Development
+
+You can run formatting, type checking and tests with [`uv`](https://github.com/astral-sh/uv).
+
+### Running tests locally
+
+GitHub Actions installs additional system packages for Qt-based tests (see `.github/workflows/tests.yml`).
+On a fresh Linux environment you can mirror that setup by running:
+
+```bash
+sudo scripts/install_test_system_deps.sh
+```
+
+Headless environments also need the same Qt variables the CI sets:
+
+```bash
+QT_API=pyside6 QT_QPA_PLATFORM=offscreen uv run pytest
+```
+
 ## License
 
 This project is licensed under a hybrid model depending on the Qt binding used:
diff --git a/fieldview/layers/text_layer.py b/fieldview/layers/text_layer.py
index 2883e6f..9291d26 100644
--- a/fieldview/layers/text_layer.py
+++ b/fieldview/layers/text_layer.py
@@ -1,4 +1,4 @@
-from typing import TYPE_CHECKING, Optional, List, Dict, Set, Union
+from typing import TYPE_CHECKING, ClassVar, Optional, List, Dict, Set, Union
 
 if TYPE_CHECKING:
     from PySide6.QtGui import QPainter, QColor, QFont, QFontMetrics, QFontDatabase
@@ -243,14 +243,54 @@ class ValueLayer(TextLayer):
     Renders numerical values.
     """
 
+    UNIT_SUFFIXES: ClassVar[tuple[str, ...]] = (
+        "℃",  # Degree Celsius
+        "℉",  # Degree Fahrenheit
+        "％",  # Percentage
+        "㎐",  # Hertz
+        "㎑",  # Kilohertz
+        "㎒",  # Megahertz
+        "㎓",  # Gigahertz
+        "㎂",  # Microampere
+        "㎃",  # Milliampere
+        "㎄",  # Kiloampere
+        "㎎",  # Milligram
+        "㎏",  # Kilogram
+        "㎍",  # Microgram
+        "㎕",  # Microliter
+        "㎖",  # Milliliter
+        "㎗",  # Deciliter
+        "㎘",  # Kiloliter
+        "㎜",  # Millimeter
+        "㎝",  # Centimeter
+        "㎞",  # Kilometer
+        "㎡",  # Square meter
+        "㎧",  # Meters per second
+        "㎨",  # Meters per second squared
+        "㎩",  # Kilopascal
+        "㎪",  # Megapascal
+        "㎫",  # Gigapascal
+        "㎷",  # Microvolt
+        "㎸",  # Millivolt
+        "㎹",  # Megavolt
+        "㎽",  # Milliampere-hour
+        "㎾",  # Kilowatt
+        "㎿",  # Megawatt
+        "㏀",  # Kiloohm
+        "㏁",  # Megaohm
+        "㏃",  # Becquerel
+        "㏄",  # Cubic centimeter
+        "㏈",  # Decibel
+        "㏊",  # Hectare
+        "㏕",  # Lux
+        "㏗",  # pH
+    )
+
     def __init__(self, data_container, parent: Optional[DataLayer] = None):
         super().__init__(data_container, parent)
         self._decimal_places = 2
-        self._suffix = ""
-        self._postfix = ""  # Same as suffix? antigravity.md says both. Let's assume prefix/suffix or just suffix.
-        # antigravity.md says "Can add suffix, postfix". Maybe prefix/suffix?
-        # Let's implement prefix and suffix.
         self._prefix = ""
+        self._postfix = ""
 
     @property
     def decimal_places(self) -> int:
@@ -263,11 +303,24 @@ def decimal_places(self, value: int):
 
     @property
     def suffix(self) -> str:
-        return self._suffix
+        return self._postfix
 
     @suffix.setter
     def suffix(self, value: str):
-        self._suffix = value
+        if not isinstance(value, str):
+            raise TypeError("Suffix must be a string")
+        self._postfix = value
+        self.update_layer()
+
+    @property
+    def postfix(self) -> str:
+        return self._postfix
+
+    @postfix.setter
+    def postfix(self, value: str):
+        if not isinstance(value, str):
+            raise TypeError("Postfix must be a string")
+        self._postfix = value
         self.update_layer()
 
     @property
@@ -276,13 +329,15 @@ def prefix(self) -> str:
 
     @prefix.setter
     def prefix(self, value: str):
+        if not isinstance(value, str):
+            raise TypeError("Prefix must be a string")
         self._prefix = value
         self.update_layer()
 
     def _get_text(self, index: int, value: Optional[float], label: str) -> str:
         if value is None:
             return ""
-        return f"{self._prefix}{value:.{self._decimal_places}f}{self._suffix}"
+        return f"{self._prefix}{value:.{self._decimal_places}f}{self._postfix}"
 
 
 class LabelLayer(TextLayer):
diff --git a/pyproject.toml b/pyproject.toml
index a02cab7..37703a2 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [project]
 name = "fieldview"
-version = "0.3.1"
+version = "0.3.2"
 description = "Python + Qt based 2D data visualization solution for irregular data points"
 readme = "README.md"
 authors = [{name = "FieldView Team", email = "dev@fieldview.org"}]
@@ -60,4 +60,3 @@ module = [
 ignore_missing_imports = true
 ignore_errors = true
 
-
diff --git a/scripts/install_test_system_deps.sh b/scripts/install_test_system_deps.sh
new file mode 100755
index 0000000..447cc46
--- /dev/null
+++ b/scripts/install_test_system_deps.sh
@@ -0,0 +1,26 @@
+#!/bin/bash
+set -euo pipefail
+
+if [[ $(id -u) -ne 0 ]]; then
+  echo "This script must be run as root (e.g., with sudo)." >&2
+  exit 1
+fi
+
+apt-get update
+apt-get install -y \
+  libegl1 \
+  libxkbcommon-x11-0 \
+  libdbus-1-3 \
+  libxcb-icccm4 \
+  libxcb-image0 \
+  libxcb-keysyms1 \
+  libxcb-randr0 \
+  libxcb-render-util0 \
+  libxcb-xinerama0 \
+  libxcb-xinput0 \
+  libxcb-xfixes0 \
+  x11-utils \
+  libxcb-cursor0 \
+  libfontconfig1 \
+  libglib2.0-0 \
+  libgl1
diff --git a/tests/test_text_layer.py b/tests/test_text_layer.py
index 0fa3eee..4ff8afc 100644
--- a/tests/test_text_layer.py
+++ b/tests/test_text_layer.py
@@ -1,5 +1,7 @@
 from typing import TYPE_CHECKING
 
+import pytest
+
 if TYPE_CHECKING:
     from PySide6.QtGui import QFont
     from PySide6.QtWidgets import QStyleOptionGraphicsItem
@@ -28,6 +30,41 @@ def test_value_layer(qtbot):
     assert layer._get_text(0, 10.12345, "") == "Val: 10.123 m"
 
 
+def test_value_layer_prefix_property_updates_layer(qtbot, monkeypatch):
+    dc = DataContainer()
+    dc.set_data([[0, 0]], [5.4321])
+    layer = ValueLayer(dc)
+
+    update_calls: list[None] = []
+    monkeypatch.setattr(layer, "update_layer", lambda: update_calls.append(None))
+
+    layer.prefix = "~"
+
+    assert layer.prefix == "~"
+    assert len(update_calls) == 1
+
+    with pytest.raises(TypeError):
+        layer.prefix = 123  # type: ignore[assignment]
+
+
+def test_value_layer_suffix_and_postfix(qtbot):
+    dc = DataContainer()
+    dc.set_data([[0, 0]], [1.2345])
+    layer = ValueLayer(dc)
+
+    layer.postfix = "㎧"
+    assert layer._get_text(0, 1.2345, "") == "1.23㎧"
+
+    layer.prefix = "~"
+    assert layer._get_text(0, 1.2345, "") == "~1.23㎧"
+
+    layer.suffix = "℃"
+    assert layer.postfix == "℃"
+    assert layer._get_text(0, 1.2345, "") == "~1.23℃"
+
+    assert "℃" in ValueLayer.UNIT_SUFFIXES
+
+
 def test_label_layer(qtbot):
     dc = DataContainer()
     dc.set_data([[0, 0]], [10], ["Test Label"])
diff --git a/uv.lock b/uv.lock
index 37f9ca6..fc7aa3b 100644
--- a/uv.lock
+++ b/uv.lock
@@ -1,5 +1,5 @@
 version = 1
-revision = 3
+revision = 2
 requires-python = ">=3.10"
 resolution-markers = [
     "python_full_version >= '3.12'",
@@ -500,7 +500,7 @@ wheels = [
 
 [[package]]
 name = "fieldview"
-version = "0.3.0"
+version = "0.3.2"
 source = { editable = "." }
 dependencies = [
     { name = "numpy" },