Move env related functionality into own package and apply proper testing

The first thing we do is moving the `util/env.go` into a new sub-package
`env/`. The package is now using an internal `impl` to be able to apply
properly mocked unit testing which is not dependent from the machine
they're running on.

Signed-off-by: Sascha Grunert <sgrunert@redhat.com>

util/env.go → env/env.go

@@ -14,24 +14,24 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-package util
+package env
 
 import (
-	"os"
+	"sigs.k8s.io/release-utils/env/internal"
 )
 
-// EnvDefault returns either the provided environment variable for the given
-// `key` or the default value `def` if not set.
-func EnvDefault(key, def string) string {
-	value, ok := os.LookupEnv(key)
+// Default returns either the provided environment variable for the given key
+// or the default value def if not set.
+func Default(key, def string) string {
+	value, ok := internal.Impl.LookupEnv(key)
 	if !ok || value == "" {
 		return def
 	}
 	return value
 }
 
-// IsEnvSet returns true if an environment variable is set
-func IsEnvSet(key string) bool {
-	_, ok := os.LookupEnv(key)
+// IsSet returns true if an environment variable is set.
+func IsSet(key string) bool {
+	_, ok := internal.Impl.LookupEnv(key)
 	return ok
 }

env/env_test.go

@@ -0,0 +1,97 @@
+/*
+Copyright 2019 The Kubernetes Authors.
+
+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
+
+    http://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 env
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"sigs.k8s.io/release-utils/env/internal"
+	"sigs.k8s.io/release-utils/env/internal/internalfakes"
+)
+
+func TestDefault(t *testing.T) {
+	for _, tc := range []struct {
+		prepare      func(*internalfakes.FakeImpl)
+		defaultValue string
+		expected     string
+	}{
+		{ // default LookupEnvReturns empty string and false
+			prepare: func(mock *internalfakes.FakeImpl) {
+				mock.LookupEnvReturns("", false)
+			},
+			defaultValue: "default",
+			expected:     "default",
+		},
+		{ // default LookupEnvReturns empty string and true
+			prepare: func(mock *internalfakes.FakeImpl) {
+				mock.LookupEnvReturns("", true)
+			},
+			defaultValue: "default",
+			expected:     "default",
+		},
+		{ // default LookupEnvReturns string and false
+			prepare: func(mock *internalfakes.FakeImpl) {
+				mock.LookupEnvReturns("value", false)
+			},
+			defaultValue: "default",
+			expected:     "default",
+		},
+		{ // value is set
+			prepare: func(mock *internalfakes.FakeImpl) {
+				mock.LookupEnvReturns("value", true)
+			},
+			defaultValue: "default",
+			expected:     "value",
+		},
+	} {
+		mock := &internalfakes.FakeImpl{}
+		tc.prepare(mock)
+		internal.Impl = mock
+
+		res := Default("key", tc.defaultValue)
+		require.Equal(t, tc.expected, res)
+	}
+}
+
+func TestIsSet(t *testing.T) {
+	for _, tc := range []struct {
+		prepare  func(*internalfakes.FakeImpl)
+		expected bool
+	}{
+		{ // LookupEnvReturns false
+			prepare: func(mock *internalfakes.FakeImpl) {
+				mock.LookupEnvReturns("", false)
+			},
+			expected: false,
+		},
+		{ // LookupEnvReturns true
+			prepare: func(mock *internalfakes.FakeImpl) {
+				mock.LookupEnvReturns("", true)
+			},
+			expected: true,
+		},
+	} {
+		mock := &internalfakes.FakeImpl{}
+		tc.prepare(mock)
+		internal.Impl = mock
+
+		res := IsSet("key")
+		require.Equal(t, tc.expected, res)
+	}
+}

env/internal/impl.go

@@ -0,0 +1,34 @@
+/*
+Copyright 2021 The Kubernetes Authors.
+
+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
+
+    http://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 internal
+
+import "os"
+
+//go:generate go run github.com/maxbrunsfeld/counterfeiter/v6 -generate
+
+//counterfeiter:generate . impl
+type impl interface {
+	LookupEnv(key string) (string, bool)
+}
+
+type defImpl struct{}
+
+var Impl impl = &defImpl{}
+
+func (defImpl) LookupEnv(key string) (string, bool) {
+	return os.LookupEnv(key)
+}