Add test case for internal/errors/observability.go (#993)

* feat: add test case and comment for observability errors

Signed-off-by: hlts2 <[email protected]>

* Update internal/errors/observability.go

* Apply suggestions from code review

Co-authored-by: Kiichiro YUKAWA <[email protected]>

* 🤖 Update license headers / Format go codes and yaml files

Signed-off-by: vdaas-ci <[email protected]>

Co-authored-by: Kiichiro YUKAWA <[email protected]>
Co-authored-by: vdaas-ci <[email protected]>

internal/errors/observability.go

@@ -17,6 +17,9 @@
 // Package errors provides error types and function
 package errors
 
-var ErrCollectorNotFound = func() error {
-	return New("observability.collector not found")
-}
+// ErrCollectorNotFound represents a function to generate an error that the observability collector is not found.
+var (
+	ErrCollectorNotFound = func() error {
+		return New("observability.collector not found")
+	}
+)

internal/errors/observability_test.go

@@ -0,0 +1,72 @@
+//
+// Copyright (C) 2019-2021 vdaas.org vald team <[email protected]>
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+package errors
+
+import (
+	"testing"
+
+	"go.uber.org/goleak"
+)
+
+func TestErrCollectorNotFound(t *testing.T) {
+	t.Parallel()
+	type want struct {
+		want error
+	}
+	type test struct {
+		name       string
+		want       want
+		checkFunc  func(want, error) error
+		beforeFunc func()
+		afterFunc  func()
+	}
+	defaultCheckFunc := func(w want, got error) error {
+		if !Is(got, w.want) {
+			return Errorf("got: \"%#v\",\n\t\t\t\twant: \"%#v\"", got, w.want)
+		}
+		return nil
+	}
+	tests := []test{
+		{
+			name: "return an ErrCollectorNotFound error",
+			want: want{
+				want: New("observability.collector not found"),
+			},
+		},
+	}
+
+	for _, tc := range tests {
+		test := tc
+		t.Run(test.name, func(tt *testing.T) {
+			tt.Parallel()
+			defer goleak.VerifyNone(tt, goleak.IgnoreCurrent())
+			if test.beforeFunc != nil {
+				test.beforeFunc()
+			}
+			if test.afterFunc != nil {
+				defer test.afterFunc()
+			}
+			if test.checkFunc == nil {
+				test.checkFunc = defaultCheckFunc
+			}
+
+			got := ErrCollectorNotFound()
+			if err := test.checkFunc(test.want, got); err != nil {
+				tt.Errorf("error = %v", err)
+			}
+		})
+	}
+}