diff --git a/travis/unit_tests/constraint_test.f90 b/travis/unit_tests/constraint_test.f90
new file mode 100644
index 000000000..dd916474e
--- /dev/null
+++ b/travis/unit_tests/constraint_test.f90
@@ -0,0 +1,29 @@
+module constraint_test
+  use fruit
+  use types_mod
+  implicit none
+
+contains
+
+  subroutine test_calcPhotolysisRaw
+    use types_mod
+    use constraint_functions_mod, only : calcPhotolysisRaw
+    use zenith_data_mod, only : cosx, secx
+    implicit none
+
+    !  photolysis = l * cosx ** m * exp( -n * secx ) * tf
+    cosx = 1.0_DP
+    secx = 1.0_DP / cosx
+    call assert_true(calcPhotolysisRaw( 1.0_DP, 1.0_DP, 1.0_DP, 1.0_DP ) == exp( -1.0_DP ),          "calcPhotolysisRaw all ones")
+    call assert_true(calcPhotolysisRaw( 2.0_DP, 1.0_DP, 1.0_DP, 1.0_DP ) == 2.0_DP * exp( -1.0_DP ), "calcPhotolysisRaw 2")
+
+    cosx = 0.5_DP
+    secx = 1.0_DP / cosx
+    call assert_true(calcPhotolysisRaw( 2.0_DP, 1.0_DP, 1.0_DP, 1.0_DP ) == exp( -2.0_DP ),          "calcPhotolysisRaw 3")
+    call assert_true(calcPhotolysisRaw( 2.0_DP, 2.0_DP, 1.0_DP, 1.0_DP ) == 0.5_DP * exp( -2.0_DP ), "calcPhotolysisRaw 4")
+    call assert_true(calcPhotolysisRaw( 2.0_DP, 1.0_DP, 2.0_DP, 1.0_DP ) == exp( -4.0_DP ),          "calcPhotolysisRaw 5")
+    call assert_true(calcPhotolysisRaw( 2.0_DP, 1.0_DP, 1.0_DP, 2.0_DP ) == 2.0_DP * exp( -2.0_DP ), "calcPhotolysisRaw 6")
+
+  end subroutine test_calcPhotolysisRaw
+
+end module constraint_test