diff --git a/HARK/tests/test_interpolation.py b/HARK/tests/test_interpolation.py
index 200b49d0e..2385b0168 100644
--- a/HARK/tests/test_interpolation.py
+++ b/HARK/tests/test_interpolation.py
@@ -9,6 +9,7 @@
 from HARK.interpolation import BilinearInterp
 from HARK.interpolation import CubicHermiteInterp as CubicInterp
 from HARK.interpolation import LinearInterp, QuadlinearInterp, TrilinearInterp
+from HARK.interpolation import IdentityFunction
 
 
 class testsLinearInterp(unittest.TestCase):
@@ -200,3 +201,46 @@ def test_same_length(self):
             self.f_array, self.w_array, self.x_array, self.y_array_t, self.z_array
         )
         self.assertEqual(bilinear(1, 2, 1, 2), 6.0)
+
+
+class test_IdentityFunction(unittest.TestCase):
+    """
+    Tests evaluation and derivatives of IdentityFunction class.
+    """
+    
+    def setUp(self):
+        self.IF1D = IdentityFunction()
+        self.IF2Da = IdentityFunction(i_dim=0, n_dims=2)
+        self.IF2Db = IdentityFunction(i_dim=1, n_dims=2)
+        self.IF3Da = IdentityFunction(i_dim=0, n_dims=3)
+        self.IF3Db = IdentityFunction(i_dim=2, n_dims=3)
+        self.X = 3*np.ones(100)
+        self.Y = 4*np.ones(100)
+        self.Z = 5*np.ones(100)
+        self.zero = np.zeros(100)
+        self.one = np.ones(100)
+        
+    def test_eval(self):
+        self.assertEqual(self.X, self.IF1D(self.X))
+        self.assertEqual(self.X, self.IF2Da(self.X, self.Y))
+        self.assertEqual(self.Y, self.IF2Db(self.X, self.Y))
+        self.assertEqual(self.X, self.IF3Da(self.X, self.Y, self.Z))
+        self.assertEqual(self.Z, self.IF3Db(self.X, self.Y, self.Z))
+        
+    def test_der(self):
+        self.assertEqual(self.one, self.IF1D.der(self.X))
+        
+        self.assertEqual(self.one, self.IF2Da.derX(self.X, self.Y))
+        self.assertEqual(self.zero, self.IF2Da.derY(self.X, self.Y))
+        
+        self.assertEqual(self.zero, self.IF2Db.derX(self.X, self.Y))
+        self.assertEqual(self.one, self.IF2Db.derY(self.X, self.Y))
+        
+        self.assertEqual(self.one, self.IF3Da.derX(self.X, self.Y, self.Z))
+        self.assertEqual(self.zero, self.IF3Da.derY(self.X, self.Y, self.Z))
+        self.assertEqual(self.zero, self.IF3Da.derZ(self.X, self.Y, self.Z))
+        
+        self.assertEqual(self.zero, self.IF3Db.derX(self.X, self.Y, self.Z))
+        self.assertEqual(self.zero, self.IF3Db.derY(self.X, self.Y, self.Z))
+        self.assertEqual(self.one, self.IF3Db.derZ(self.X, self.Y, self.Z))
+        
\ No newline at end of file