1 files changed, 22 insertions, 0 deletions
diff --git a/src/test/java/org/shedlang/compiler/types/TypeSubstitutionTests.java b/src/test/java/org/shedlang/compiler/types/TypeSubstitutionTests.java
index 210e4c18..c53038ca 100644
--- a/src/test/java/org/shedlang/compiler/types/TypeSubstitutionTests.java
+++ b/src/test/java/org/shedlang/compiler/types/TypeSubstitutionTests.java
@@ -42,6 +42,28 @@ public class TypeSubstitutionTests {
     }
 
     @Test
+    public void substitutingEffectIoDoesNothing() {
+        var typeSubstitutionMap = TypeSubstitutionMap.of(
+            Map.entry(EffectParam.forStructType(STRUCT_TYPE, "E"), Effects.NONE)
+        );
+
+        var result = TypeSubstitution.substituteEffect(Effects.IO, typeSubstitutionMap);
+
+        assertThat(result, equalTo(Effects.IO));
+    }
+
+    @Test
+    public void substitutingEffectNoneDoesNothing() {
+        var typeSubstitutionMap = TypeSubstitutionMap.of(
+            Map.entry(EffectParam.forStructType(STRUCT_TYPE, "E"), Effects.IO)
+        );
+
+        var result = TypeSubstitution.substituteEffect(Effects.NONE, typeSubstitutionMap);
+
+        assertThat(result, equalTo(Effects.NONE));
+    }
+
+    @Test
     public void substitutingBoolDoesNothing() {
         var typeSubstitutionMap = TypeSubstitutionMap.of(
             Map.entry(TypeParam.forStructType(STRUCT_TYPE, "T"), Types.INT)