diff --git a/coverage-report.pdf b/coverage-report.pdf
new file mode 100644
index 0000000..f42160b
Binary files /dev/null and b/coverage-report.pdf differ
diff --git a/diffusion2d.py b/diffusion2d.py
index 51a07f2..17bc002 100644
--- a/diffusion2d.py
+++ b/diffusion2d.py
@@ -38,6 +38,10 @@ def __init__(self):
         self.dt = None
 
     def initialize_domain(self, w=10., h=10., dx=0.1, dy=0.1):
+        assert isinstance(w, float), "w must be a float"
+        assert isinstance(h, float), "h must be a float"
+        assert isinstance(dx, float), "dx must be a float"
+        assert isinstance(dy, float), "dy must be a float"
         self.w = w
         self.h = h
         self.dx = dx
@@ -45,7 +49,10 @@ def initialize_domain(self, w=10., h=10., dx=0.1, dy=0.1):
         self.nx = int(w / dx)
         self.ny = int(h / dy)
 
-    def initialize_physical_parameters(self, d=4., T_cold=300, T_hot=700):
+    def initialize_physical_parameters(self, d=4., T_cold=300., T_hot=700.):
+        assert isinstance(d, float), "d must be a float"
+        assert isinstance(T_cold, float), "T_cold must be a float"
+        assert isinstance(T_hot, float), "T_hot must be a float"
         self.D = d
         self.T_cold = T_cold
         self.T_hot = T_hot
diff --git a/requirements.txt b/requirements.txt
new file mode 100644
index 0000000..7851745
--- /dev/null
+++ b/requirements.txt
@@ -0,0 +1,3 @@
+pytest
+numpy
+matplotlib
\ No newline at end of file
diff --git a/tests/integration/test_diffusion2d.py b/tests/integration/test_diffusion2d.py
index fd026b4..9278aae 100644
--- a/tests/integration/test_diffusion2d.py
+++ b/tests/integration/test_diffusion2d.py
@@ -3,7 +3,8 @@
 """
 
 from diffusion2d import SolveDiffusion2D
-
+import pytest
+import numpy as np
 
 def test_initialize_physical_parameters():
     """
@@ -11,9 +12,42 @@ def test_initialize_physical_parameters():
     """
     solver = SolveDiffusion2D()
 
+    expected_dt = 0.0005
+
+    solver.initialize_domain(10., 10., 0.1, 0.1)
+    solver.initialize_physical_parameters(5.,350.,750.)
+
+    assert solver.dt == pytest.approx(expected_dt, abs=1e-4)
+
 
 def test_set_initial_condition():
     """
     Checks function SolveDiffusion2D.get_initial_function
     """
     solver = SolveDiffusion2D()
+
+    w = 20.
+    h = 20.
+    dx = 0.2
+    dy = 0.2
+    nx = int(w / dx)
+    ny = int(h / dy)
+    T_cold = 350.
+    T_hot = 750.
+
+    u = T_cold * np.ones((nx, ny))
+
+    # Initial conditions - circle of radius r centred at (cx,cy) (mm)
+    r, cx, cy = 2, 5, 5
+    r2 = r ** 2
+    for i in range(nx):
+        for j in range(ny):
+            p2 = (i * dx - cx) ** 2 + (j * dy - cy) ** 2
+            if p2 < r2:
+                u[i, j] = T_hot
+
+    solver.initialize_domain(w, h, dx, dy)
+    solver.initialize_physical_parameters(5., 350., 750.)
+    solver_u = solver.set_initial_condition()
+
+    assert solver_u == pytest.approx(u, abs=1e-4)
diff --git a/tests/unit/test_diffusion2d_functions.py b/tests/unit/test_diffusion2d_functions.py
index c4277ff..7fb6507 100644
--- a/tests/unit/test_diffusion2d_functions.py
+++ b/tests/unit/test_diffusion2d_functions.py
@@ -1,6 +1,8 @@
 """
 Tests for functions in class SolveDiffusion2D
 """
+import numpy as np
+import pytest
 
 from diffusion2d import SolveDiffusion2D
 
@@ -10,6 +12,17 @@ def test_initialize_domain():
     Check function SolveDiffusion2D.initialize_domain
     """
     solver = SolveDiffusion2D()
+    w = 20.
+    h = 20.
+    dx=0.2
+    dy=0.2
+
+    expected_nx = 100
+    expected_ny = 100
+
+    solver.initialize_domain(w,h,dx,dy)
+    assert solver.nx == expected_nx, "value of nx is wrong, did the calculation change?"
+    assert solver.ny == expected_ny, "value of ny is wrong, did the calculation change?"
 
 
 def test_initialize_physical_parameters():
@@ -18,9 +31,53 @@ def test_initialize_physical_parameters():
     """
     solver = SolveDiffusion2D()
 
+    d = 5.
+    T_cold = 350.
+    T_hot = 750.
+    solver.dx = 0.1
+    solver.dy = 0.1
+
+    expected_dt = 0.0005
+
+    solver.initialize_physical_parameters(d, T_cold, T_hot)
+    assert solver.dt == pytest.approx(expected_dt, abs=1e-4)
+
 
 def test_set_initial_condition():
     """
     Checks function SolveDiffusion2D.get_initial_function
     """
     solver = SolveDiffusion2D()
+
+    w = 20.
+    h = 20.
+    dx = 0.2
+    dy = 0.2
+    nx = int(w / dx)
+    ny = int(h / dy)
+    T_cold = 350.
+    T_hot = 750.
+
+    u = T_cold * np.ones((nx, ny))
+
+    # Initial conditions - circle of radius r centred at (cx,cy) (mm)
+    r, cx, cy = 2, 5, 5
+    r2 = r ** 2
+    for i in range(nx):
+        for j in range(ny):
+            p2 = (i * dx - cx) ** 2 + (j * dy - cy) ** 2
+            if p2 < r2:
+                u[i, j] = T_hot
+
+    solver.T_cold = T_cold
+    solver.T_hot = T_hot
+    solver.w = w
+    solver.h = h
+    solver.dx = dx
+    solver.dy = dy
+    solver.nx = nx
+    solver.ny = ny
+
+    solver_u = solver.set_initial_condition()
+
+    assert solver_u == pytest.approx(u, abs=1e-4)
diff --git a/tox.toml b/tox.toml
new file mode 100644
index 0000000..e7f4fac
--- /dev/null
+++ b/tox.toml
@@ -0,0 +1,7 @@
+requires = ["tox>=4"]
+env_list = ["pytest_testing"]
+
+[env.pytest_testing]
+description = "Run pytest"
+deps = ["-rrequirements.txt"]
+commands = [["python", "-m", "pytest"]]
\ No newline at end of file