Improve failure messages for some error asserters

ccoVeille · ccoVeille · commit 4b9713bfda2d · 2025-05-08T16:13:52.000+02:00
The following changes were made to improve the error messages

- ErrorIs now reports clearly the target error is nil
- NotErrorIs now reports the target error is nil
- ErrorAs now reports clearly the tested error is nil
diff --git a/assert/assertions.go b/assert/assertions.go
@@ -2202,11 +2202,17 @@ func ErrorAs(t TestingT, err error, target interface{}, msgAndArgs ...interface{
 		return true
 	}
 
+	expectedText := reflect.ValueOf(target).Elem().Type().String()
+	if err == nil {
+		return Fail(t, fmt.Sprintf("An error is expected but got nil.\n"+
+			"expected: %s", expectedText), msgAndArgs...)
+	}
+
 	chain := buildErrorChainString(err, true)
 
 	return Fail(t, fmt.Sprintf("Should be in error chain:\n"+
 		"expected: %s\n"+
-		"in chain: %s", reflect.ValueOf(target).Elem().Type(), chain,
+		"in chain: %s", expectedText, chain,
 	), msgAndArgs...)
 }
 
diff --git a/assert/assertions_test.go b/assert/assertions_test.go
@@ -3402,9 +3402,8 @@ func TestErrorAs(t *testing.T) {
 			err:    nil,
 			result: false,
 			resultErrMsg: "" +
-				"Should be in error chain:\n" +
-				"expected: *assert.customError\n" +
-				"in chain: \n",
+				"An error is expected but got nil.\n" +
+				`expected: *assert.customError` + "\n",
 		},
 		{
 			err:    fmt.Errorf("abc: %w", errors.New("def")),
