diff --git a/src/lib.rs b/src/lib.rs
index 4ad95f1..546fef3 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -5,3 +5,6 @@ pub mod gadgets;
 pub mod layers;
 pub mod model;
 pub mod utils;
+
+#[cfg(test)]
+pub mod tests;
diff --git a/src/tests/mod.rs b/src/tests/mod.rs
new file mode 100644
index 0000000..ea5c4e0
--- /dev/null
+++ b/src/tests/mod.rs
@@ -0,0 +1,2 @@
+pub mod sqrt;
+pub mod test_circuit;
diff --git a/src/tests/sqrt.rs b/src/tests/sqrt.rs
new file mode 100644
index 0000000..3445449
--- /dev/null
+++ b/src/tests/sqrt.rs
@@ -0,0 +1,61 @@
+use std::{
+  collections::{HashMap, HashSet},
+  marker::PhantomData,
+};
+
+use halo2_proofs::{
+  circuit::{AssignedCell, Layouter, Value},
+  dev::MockProver,
+  halo2curves::{bn256::Fr, FieldExt},
+};
+use ndarray::{Array, ArrayBase, Dim, IxDyn, IxDynImpl, OwnedRepr};
+
+use crate::gadgets::gadget::Gadget;
+use crate::{
+  gadgets::{
+    gadget::{self, GadgetConfig, GadgetType},
+    sqrt_big::SqrtBigChip,
+  },
+  tests::test_circuit::{TestCircuit, K},
+  utils::loader::TensorMsgpack,
+};
+
+use super::test_circuit::{TestCircFunc, TestConfig};
+
+pub struct TestFunc {}
+
+impl<F: FieldExt> TestCircFunc<F> for TestFunc {
+  fn compute_tensor(
+    layouter: &mut impl Layouter<F>,
+    config: &TestConfig<F>,
+    tensors: &Vec<ArrayBase<OwnedRepr<AssignedCell<F, F>>, Dim<IxDynImpl>>>,
+    constants: &HashMap<i64, AssignedCell<F, F>>,
+  ) {
+    let inp = &tensors[0];
+    let inp_vec = inp.iter().collect::<Vec<_>>();
+
+    let zero = constants.get(&0).unwrap().clone();
+
+    let sqrt_chip = SqrtBigChip::<F>::construct(config.gadget_config.clone().into());
+    let _result = sqrt_chip.forward(layouter.namespace(|| "test"), &vec![inp_vec], &vec![zero]);
+  }
+}
+
+#[test]
+fn test_sqrt() {
+  let input_tensor = TensorMsgpack {
+    idx: 0,
+    shape: vec![3],
+    data: vec![5, 10, 100],
+  };
+  let input_tensors: Vec<TensorMsgpack> = vec![input_tensor];
+
+  let gadget = &crate::tests::test_circuit::GADGET_CONFIG;
+  let cloned_gadget = gadget.lock().unwrap().clone();
+
+  let circuit = TestCircuit::<Fr, TestFunc>::new(input_tensors);
+
+  let outp = vec![];
+  let prover = MockProver::run(K.try_into().unwrap(), &circuit, vec![outp.clone()]).unwrap();
+  assert_eq!(prover.verify(), Ok(()));
+}
diff --git a/src/tests/test_circuit.rs b/src/tests/test_circuit.rs
new file mode 100644
index 0000000..01d04f8
--- /dev/null
+++ b/src/tests/test_circuit.rs
@@ -0,0 +1,321 @@
+use halo2_proofs::{dev::MockProver, halo2curves::bn256::Fr};
+use std::{
+  collections::{HashMap, HashSet},
+  marker::PhantomData,
+  rc::Rc,
+  sync::Mutex,
+};
+
+use halo2_proofs::{
+  circuit::{AssignedCell, Layouter, SimpleFloorPlanner, Value},
+  halo2curves::FieldExt,
+  plonk::{Advice, Circuit, Column, ConstraintSystem, Error},
+};
+use lazy_static::lazy_static;
+use ndarray::{Array, IxDyn};
+
+use crate::{
+  gadgets::{
+    add_pairs::AddPairsChip,
+    adder::AdderChip,
+    bias_div_round_relu6::BiasDivRoundRelu6Chip,
+    dot_prod::DotProductChip,
+    gadget::{Gadget, GadgetConfig, GadgetType},
+    mul_pairs::MulPairsChip,
+    nonlinear::exp::ExpChip,
+    nonlinear::{logistic::LogisticGadgetChip, rsqrt::RsqrtGadgetChip},
+    sqrt_big::SqrtBigChip,
+    squared_diff::SquaredDiffGadgetChip,
+    sub_pairs::SubPairsChip,
+    var_div::VarDivRoundChip,
+  },
+  layers::{
+    dag::{DAGLayerChip, DAGLayerConfig},
+    layer::{Layer, LayerConfig, LayerType},
+  },
+  utils::loader::{load_model_msgpack, ModelMsgpack},
+};
+
+//
+// Contains a way to unit-test each of the files
+//
+
+// Note this useful idiom: importing names from outer (for mod tests) scope.
+use super::*;
+use crate::{gadgets::sqrt_big, utils::loader::TensorMsgpack};
+use ndarray::{ArrayBase, Dim, IxDynImpl, OwnedRepr};
+
+pub const K: u64 = 19;
+pub const GLOBAL_SF: i64 = 2 ^ 16;
+pub const NUM_COLS: u64 = 6;
+
+lazy_static! {
+  pub static ref GADGET_CONFIG: Mutex<GadgetConfig> = Mutex::new(GadgetConfig::default());
+}
+
+pub trait TestCircFunc<F: FieldExt> {
+  fn compute_tensor(
+    layouter: &mut impl Layouter<F>,
+    config: &TestConfig<F>,
+    tensors: &Vec<ArrayBase<OwnedRepr<AssignedCell<F, F>>, Dim<IxDynImpl>>>,
+    hash_map: &HashMap<i64, AssignedCell<F, F>>,
+  );
+}
+
+#[derive(Clone, Debug)]
+pub struct TestCircuit<F: FieldExt, G: TestCircFunc<F>> {
+  pub used_gadgets: HashSet<GadgetType>,
+  pub tensors: HashMap<i64, Array<Value<F>, IxDyn>>,
+  pub _marker: PhantomData<F>,
+  pub _func_marker: PhantomData<G>,
+}
+
+impl<F: FieldExt, G: TestCircFunc<F>> TestCircuit<F, G> {
+  pub fn new(input_tensors: Vec<TensorMsgpack>) -> Self {
+    let gadget = &GADGET_CONFIG;
+    let cloned_gadget = gadget.lock().unwrap().clone();
+    *gadget.lock().unwrap() = GadgetConfig {
+      scale_factor: GLOBAL_SF as u64,
+      shift_min_val: -(GLOBAL_SF * GLOBAL_SF * 1024),
+      div_outp_min_val: -(1 << (K - 1)),
+      min_val: -(1 << (K - 1)),
+      max_val: (1 << (K - 1)) - 10,
+      num_rows: (1 << K) - 10,
+      num_cols: NUM_COLS as usize,
+      ..cloned_gadget
+    };
+
+    let to_value = |x: i64| {
+      let bias = 1 << 31;
+      let x_pos = x + bias;
+      Value::known(F::from(x_pos as u64)) - Value::known(F::from(bias as u64))
+    };
+
+    let mut tensors = HashMap::new();
+
+    for flat in input_tensors {
+      let value_flat = flat.data.iter().map(|x| to_value(*x)).collect::<Vec<_>>();
+      let shape = flat.shape.iter().map(|x| *x as usize).collect::<Vec<_>>();
+      let tensor = Array::from_shape_vec(IxDyn(&shape), value_flat).unwrap();
+      tensors.insert(flat.idx, tensor);
+    }
+
+    let mut used_gadgets = HashSet::new();
+    used_gadgets.insert(GadgetType::AddPairs);
+    used_gadgets.insert(GadgetType::Adder);
+    used_gadgets.insert(GadgetType::BiasDivRoundRelu6);
+    used_gadgets.insert(GadgetType::DotProduct);
+    used_gadgets.insert(GadgetType::Rsqrt);
+    used_gadgets.insert(GadgetType::Exp);
+    used_gadgets.insert(GadgetType::Logistic);
+
+    Self {
+      used_gadgets: used_gadgets,
+      tensors: tensors,
+      _marker: PhantomData,
+      _func_marker: PhantomData,
+    }
+  }
+
+  pub fn assign_tensors(
+    &self,
+    mut layouter: impl Layouter<F>,
+    columns: &Vec<Column<Advice>>,
+    tensors: &HashMap<i64, Array<Value<F>, IxDyn>>,
+  ) -> Result<Vec<Array<AssignedCell<F, F>, IxDyn>>, Error> {
+    let tensors = layouter.assign_region(
+      || "asssignment",
+      |mut region| {
+        let mut cell_idx = 0;
+        let mut assigned_tensors = vec![];
+
+        for (tensor_idx, tensor) in tensors {
+          let tensor_idx = *tensor_idx as usize;
+          let mut flat = vec![];
+          for val in tensor.iter() {
+            let row_idx = cell_idx / columns.len();
+            let col_idx = cell_idx % columns.len();
+            let cell = region.assign_advice(|| "assignment", columns[col_idx], row_idx, || *val)?;
+            flat.push(cell);
+            cell_idx += 1;
+          }
+          let tensor = Array::from_shape_vec(tensor.shape(), flat).unwrap();
+          // TODO: is there a non-stupid way to do this?
+          while assigned_tensors.len() <= tensor_idx {
+            assigned_tensors.push(tensor.clone());
+          }
+          assigned_tensors[tensor_idx] = tensor;
+        }
+
+        Ok(assigned_tensors)
+      },
+    )?;
+
+    Ok(tensors)
+  }
+
+  // FIXME: assign to public
+  pub fn assign_constants(
+    &self,
+    mut layouter: impl Layouter<F>,
+    model_config: &TestConfig<F>,
+  ) -> Result<HashMap<i64, AssignedCell<F, F>>, Error> {
+    let sf = model_config.gadget_config.scale_factor;
+    let min_val = model_config.gadget_config.min_val;
+    let max_val = model_config.gadget_config.max_val;
+
+    let constants = layouter.assign_region(
+      || "constants",
+      |mut region| {
+        let mut constants: HashMap<i64, AssignedCell<F, F>> = HashMap::new();
+        let zero = region.assign_fixed(
+          || "zero",
+          model_config.gadget_config.fixed_columns[0],
+          0,
+          || Value::known(F::zero()),
+        )?;
+        let one = region.assign_fixed(
+          || "one",
+          model_config.gadget_config.fixed_columns[0],
+          1,
+          || Value::known(F::one()),
+        )?;
+        let sf_cell = region.assign_fixed(
+          || "sf",
+          model_config.gadget_config.fixed_columns[0],
+          2,
+          || Value::known(F::from(sf)),
+        )?;
+        let min_val_cell = region.assign_fixed(
+          || "min_val",
+          model_config.gadget_config.fixed_columns[0],
+          3,
+          || Value::known(F::zero() - F::from((-min_val) as u64)),
+        )?;
+        // TODO: the table goes from min_val to max_val - 1... fix this
+        let max_val_cell = region.assign_fixed(
+          || "max_val",
+          model_config.gadget_config.fixed_columns[0],
+          4,
+          || Value::known(F::from((max_val - 1) as u64)),
+        )?;
+
+        constants.insert(0, zero);
+        constants.insert(1, one);
+        constants.insert(sf as i64, sf_cell);
+        constants.insert(min_val, min_val_cell);
+        constants.insert(max_val, max_val_cell);
+        Ok(constants)
+      },
+    )?;
+    Ok(constants)
+  }
+}
+
+impl<F: FieldExt, G: TestCircFunc<F>> Circuit<F> for TestCircuit<F, G> {
+  type Config = TestConfig<F>;
+  type FloorPlanner = SimpleFloorPlanner;
+
+  fn without_witnesses(&self) -> Self {
+    todo!()
+  }
+
+  fn configure(meta: &mut ConstraintSystem<F>) -> Self::Config {
+    // FIXME: decide which gadgets to make
+    let mut gadget_config = GADGET_CONFIG.lock().unwrap().clone();
+
+    let columns = (0..gadget_config.num_cols)
+      .map(|_| meta.advice_column())
+      .collect::<Vec<_>>();
+    for col in columns.iter() {
+      meta.enable_equality(*col);
+    }
+    gadget_config.columns = columns;
+
+    gadget_config.public_columns = vec![meta.instance_column()];
+    meta.enable_equality(gadget_config.public_columns[0]);
+
+    gadget_config.fixed_columns = vec![meta.fixed_column()];
+    meta.enable_equality(gadget_config.fixed_columns[0]);
+
+    // FIXME: fix this shit
+    gadget_config = AddPairsChip::<F>::configure(meta, gadget_config);
+    gadget_config = AdderChip::<F>::configure(meta, gadget_config);
+    gadget_config = BiasDivRoundRelu6Chip::<F>::configure(meta, gadget_config);
+    gadget_config = DotProductChip::<F>::configure(meta, gadget_config);
+    gadget_config = VarDivRoundChip::<F>::configure(meta, gadget_config);
+    gadget_config = RsqrtGadgetChip::<F>::configure(meta, gadget_config);
+    gadget_config = MulPairsChip::<F>::configure(meta, gadget_config);
+    gadget_config = SubPairsChip::<F>::configure(meta, gadget_config);
+    gadget_config = ExpChip::<F>::configure(meta, gadget_config);
+    gadget_config = LogisticGadgetChip::<F>::configure(meta, gadget_config);
+    gadget_config = SquaredDiffGadgetChip::<F>::configure(meta, gadget_config);
+    gadget_config = SqrtBigChip::<F>::configure(meta, gadget_config);
+
+    TestConfig {
+      gadget_config: gadget_config.into(),
+      _marker: PhantomData,
+    }
+  }
+
+  fn synthesize(&self, config: Self::Config, mut layouter: impl Layouter<F>) -> Result<(), Error> {
+    // Assign tables
+    let gadget_rc: Rc<GadgetConfig> = config.gadget_config.clone().into();
+
+    for gadget in self.used_gadgets.iter() {
+      match gadget {
+        GadgetType::AddPairs => {
+          let chip = AddPairsChip::<F>::construct(gadget_rc.clone());
+          chip.load_lookups(layouter.namespace(|| "add pairs lookup"))?;
+        }
+        GadgetType::Adder => {
+          let chip = AdderChip::<F>::construct(gadget_rc.clone());
+          chip.load_lookups(layouter.namespace(|| "adder lookup"))?;
+        }
+        GadgetType::BiasDivRoundRelu6 => {
+          let chip = BiasDivRoundRelu6Chip::<F>::construct(gadget_rc.clone());
+          chip.load_lookups(layouter.namespace(|| "bias div round relu6 lookup"))?;
+        }
+        GadgetType::DotProduct => {
+          let chip = DotProductChip::<F>::construct(gadget_rc.clone());
+          chip.load_lookups(layouter.namespace(|| "dot product lookup"))?;
+        }
+        GadgetType::VarDivRound => {
+          let chip = VarDivRoundChip::<F>::construct(gadget_rc.clone());
+          chip.load_lookups(layouter.namespace(|| "var div lookup"))?;
+        }
+        GadgetType::Rsqrt => {
+          let chip = RsqrtGadgetChip::<F>::construct(gadget_rc.clone());
+          chip.load_lookups(layouter.namespace(|| "rsqrt lookup"))?;
+        }
+        GadgetType::Exp => {
+          let chip = ExpChip::<F>::construct(gadget_rc.clone());
+          chip.load_lookups(layouter.namespace(|| "exp lookup"))?;
+        }
+        GadgetType::Logistic => {
+          let chip = LogisticGadgetChip::<F>::construct(gadget_rc.clone());
+          chip.load_lookups(layouter.namespace(|| "logistic lookup"))?;
+        }
+        _ => panic!("unsupported gadget"),
+      }
+    }
+
+    // Assign weights and constants
+    let tensors = self.assign_tensors(
+      layouter.namespace(|| "assignment"),
+      &config.gadget_config.columns,
+      &self.tensors,
+    )?;
+    let constants = self.assign_constants(layouter.namespace(|| "constants"), &config)?;
+
+    G::compute_tensor(&mut layouter, &config, &tensors, &constants);
+
+    Ok(())
+  }
+}
+
+#[derive(Clone, Debug)]
+pub struct TestConfig<F: FieldExt> {
+  pub gadget_config: Rc<GadgetConfig>,
+  pub _marker: PhantomData<F>,
+}