add tests and godoc

Author: PeterIvanov

error_113_test.go

@@ -34,13 +34,15 @@ func TestErrorUnwrap(t *testing.T) {
 		unwrapped := errors.Unwrap(err)
 		require.NotNil(t, unwrapped)
 		require.True(t, IsOfType(unwrapped, testType))
+		require.True(t, Cast(unwrapped).Type() == testType)
 	})
 
 	t.Run("DecorateForeign", func(t *testing.T) {
 		err := Decorate(io.EOF, "")
 		unwrapped := errors.Unwrap(err)
 		require.NotNil(t, unwrapped)
 		require.True(t, errors.Is(unwrapped, io.EOF))
+		require.True(t, unwrapped == io.EOF)
 	})
 
 	t.Run("Nested", func(t *testing.T) {
@@ -79,26 +81,25 @@ func TestErrorIs(t *testing.T) {
 	})
 
 	t.Run("Wrap", func(t *testing.T) {
-		err := testTypeBar1.Wrap(testType.NewWithNoMessage(),"")
+		err := testTypeBar1.Wrap(testType.NewWithNoMessage(), "")
 		require.False(t, errors.Is(err, testType.NewWithNoMessage()))
 		require.True(t, errors.Is(err, testTypeBar1.NewWithNoMessage()))
 	})
 
 	t.Run("Supertype", func(t *testing.T) {
-		err := testSubtype0.Wrap(testTypeBar1.NewWithNoMessage(),"")
+		err := testSubtype0.Wrap(testTypeBar1.NewWithNoMessage(), "")
 		require.True(t, errors.Is(err, testType.NewWithNoMessage()))
 		require.True(t, errors.Is(err, testSubtype0.NewWithNoMessage()))
 		require.False(t, errors.Is(err, testTypeBar1.NewWithNoMessage()))
 	})
 
 	t.Run("Decorate", func(t *testing.T) {
-		err := Decorate(testType.NewWithNoMessage(),"")
+		err := Decorate(testType.NewWithNoMessage(), "")
 		require.True(t, errors.Is(err, testType.NewWithNoMessage()))
 	})
 
 	t.Run("DecorateForeign", func(t *testing.T) {
-		err := Decorate(io.EOF,"")
+		err := Decorate(io.EOF, "")
 		require.True(t, errors.Is(err, io.EOF))
 	})
 }
-

type.go

@@ -56,7 +56,7 @@ func (t *Type) NewWithNoMessage() *Error {
 // The original error will not pass its dynamic properties, and those are accessible only via direct walk over Cause() chain.
 // Without args, leaves the original message intact, so a message may be generated or provided externally.
 // With args, a formatting is performed, and it is therefore expected a format string to be constant.
-// NB: Wrap is NOT the reverse of Error.Unwrap method; name may be changed in future releases to avoid confusion.
+// NB: Wrap is NOT the reverse of errors.Unwrap() or Error.Unwrap() method; name may be changed in future releases to avoid confusion.
 func (t *Type) Wrap(err error, message string, args ...interface{}) *Error {
 	return NewErrorBuilder(t).
 		WithConditionallyFormattedMessage(message, args...).