diff --git a/tests/hlsl/inverse-trig.shader_test b/tests/hlsl/inverse-trig.shader_test
index 6077b4b5..dd069fef 100644
--- a/tests/hlsl/inverse-trig.shader_test
+++ b/tests/hlsl/inverse-trig.shader_test
@@ -90,3 +90,107 @@ probe all rgba (10472.0, 0.0, 0.0, 0.0) 4096
 uniform 0 float4 1.0 0.0 0.0 0.0
 todo draw quad
 probe all rgba (31416.0, 0.0, 0.0, 0.0)
+
+
+[pixel shader todo]
+uniform float4 a;
+
+float4 main() : sv_target
+{
+    return float4(atan(a.x), 0.0, 0.0, 0.0);
+}
+
+[test]
+uniform 0 float4 -1.0 0.0 0.0 0.0
+todo draw quad
+probe all rgba (-0.785409629, 0.0, 0.0, 0.0) 512
+
+uniform 0 float4 -0.5 0.0 0.0 0.0
+todo draw quad
+probe all rgba (-0.4636476, 0.0, 0.0, 0.0) 256
+
+uniform 0 float4 0.0 0.0 0.0 0.0
+todo draw quad
+probe all rgba (0.0, 0.0, 0.0, 0.0) 256
+
+uniform 0 float4 0.5 0.0 0.0 0.0
+todo draw quad
+probe all rgba (0.4636476, 0.0, 0.0, 0.0) 256
+
+uniform 0 float4 1.0 0.0 0.0 0.0
+todo draw quad
+probe all rgba (0.785409629, 0.0, 0.0, 0.0) 512
+
+[pixel shader todo]
+uniform float4 a;
+
+float4 main() : sv_target
+{
+    // The argument order is (y,x), and test case inputs are (y,x) also.
+    return float4(atan2(a.x, a.y), 0.0, 0.0, 0.0);
+}
+
+[test]
+% Non-degenerate cases
+uniform 0 float4 1.0 1.0 0.0 0.0
+todo draw quad
+probe all rgba (0.785385, 0.0, 0.0, 0.0) 512
+
+uniform 0 float4 5.0 -5.0 0.0 0.0
+todo draw quad
+probe all rgba (2.356194, 0.0, 0.0, 0.0) 256
+
+uniform 0 float4 -3.0 -3.0 0.0 0.0
+todo draw quad
+probe all rgba (-2.356194, 0.0, 0.0, 0.0) 256
+
+uniform 0 float4 1.0 0.0 0.0 0.0
+todo draw quad
+probe all rgba (1.570796, 0.0, 0.0, 0.0) 256
+
+uniform 0 float4 -1.0 0.0 0.0 0.0
+todo draw quad
+probe all rgba (-1.570796, 0.0, 0.0, 0.0) 256
+
+uniform 0 float4 0.0 1.0 0.0 0.0
+todo draw quad
+probe all rgba (0.0, 0.0, 0.0, 0.0) 256
+
+uniform 0 float4 0.0 -1.0 0.0 0.0
+todo draw quad
+probe all rgba (3.1415927, 0.0, 0.0, 0.0) 256
+
+% Degenerate cases
+uniform 0 float4 0.00001 0.00002 0.0 0.0
+todo draw quad
+probe all rgba (0.463647, 0.0, 0.0, 0.0) 256
+
+uniform 0 float4 0.00001 -0.00002 0.0 0.0
+todo draw quad
+probe all rgba (2.677945, 0.0, 0.0, 0.0) 256
+
+uniform 0 float4 -0.00001 100000.0 0.0 0.0
+todo draw quad
+probe all rgba (-0.000000000099986595, 0.0, 0.0, 0.0) 2048
+
+uniform 0 float4 10000000.0 0.00000001 0.0 0.0
+todo draw quad
+probe all rgba (1.570796, 0.0, 0.0, 0.0) 256
+
+% Negative zero behavior should be to treat it the
+% same as normal zero.
+uniform 0 float4 1000000000.0 0.0 0.0 0.0
+todo draw quad
+probe all rgba (1.570796, 0.0, 0.0, 0.0) 256
+
+uniform 0 float4 1000000000.0 -0.0 0.0 0.0
+todo draw quad
+probe all rgba (1.570796, 0.0, 0.0, 0.0) 256
+
+uniform 0 float4 0.0 -1.0 0.0 0.0
+todo draw quad
+probe all rgba (3.1415927, 0.0, 0.0, 0.0) 256
+
+uniform 0 float4 -0.0 -1.0 0.0 0.0
+todo draw quad
+probe all rgba (3.1415927, 0.0, 0.0, 0.0) 256