assert: add ErrorIs function

assert/assert.go

@@ -2,6 +2,7 @@
 package assert
 
 import (
+	"errors"
 	"fmt"
 	"reflect"
 	"testing"
@@ -47,6 +48,23 @@ func Error(t *testing.T, err error, expectedError string, errorMessage ...string
 	fail(t, msg, errorMessage...)
 }
 
+// ErrorIs asserts that a function returned an error that matches the specified error.
+func ErrorIs(t *testing.T, err, expectedError error, errorMessage ...string) {
+	t.Helper()
+	if err == nil {
+		msg := fmt.Sprintf("Error not returned: \nexpected: %v\nactual  : nil", expectedError)
+		fail(t, msg, errorMessage...)
+		return
+	}
+
+	if errors.Is(err, expectedError) {
+		return
+	}
+
+	msg := fmt.Sprintf("Error not equal: \nexpected: %v\nactual  : %v", expectedError, err)
+	fail(t, msg, errorMessage...)
+}
+
 // True asserts that the specified value is true.
 func True(t *testing.T, value bool, errorMessage ...string) {
 	t.Helper()

assert/assert_test.go

@@ -1,6 +1,37 @@
 package assert
 
-import "testing"
+import (
+	"errors"
+	"fmt"
+	"testing"
+)
+
+func TestEqual(t *testing.T) {
+	Equal(t, 1, 1)
+}
+
+func TestNoError(t *testing.T) {
+	NoError(t, nil)
+}
+
+func TestError(t *testing.T) {
+	err := errors.New("error text")
+	Error(t, err, err.Error())
+}
+
+func TestErrorIs(t *testing.T) {
+	errTest := errors.New("error")
+	err := fmt.Errorf("error: %w", errTest)
+	ErrorIs(t, err, errTest)
+}
+
+func TestTrue(t *testing.T) {
+	True(t, true)
+}
+
+func TestFalse(t *testing.T) {
+	False(t, false)
+}
 
 func TestInterfaceNilEqual(t *testing.T) {
 	var values []int