Add env package for testable environment variable access

env/env.go

@@ -0,0 +1,23 @@
+// SPDX-FileCopyrightText: Copyright 2025 Stacklok, Inc.
+// SPDX-License-Identifier: Apache-2.0
+
+// Package env provides abstractions for environment variable access
+// to enable dependency injection and testing isolation.
+package env
+
+//go:generate mockgen -source=env.go -destination=mocks/mock_reader.go -package=mocks Reader
+
+import "os"
+
+// Reader defines an interface for environment variable access
+type Reader interface {
+	Getenv(key string) string
+}
+
+// OSReader implements Reader using the standard os package
+type OSReader struct{}
+
+// Getenv returns the value of the environment variable named by the key
+func (*OSReader) Getenv(key string) string {
+	return os.Getenv(key)
+}

env/env_test.go

@@ -0,0 +1,67 @@
+// SPDX-FileCopyrightText: Copyright 2025 Stacklok, Inc.
+// SPDX-License-Identifier: Apache-2.0
+
+package env
+
+import (
+	"os"
+	"testing"
+)
+
+func TestOSReader_Getenv(t *testing.T) { //nolint:paralleltest // Modifies environment variables
+	// Cannot run in parallel because it modifies environment variables
+	testKey := "TEST_ENV_VARIABLE_FOR_TESTING"
+	testValue := "test_value_123"
+
+	// Set an environment variable for testing
+	originalValue, wasSet := os.LookupEnv(testKey)
+	os.Setenv(testKey, testValue)
+	t.Cleanup(func() {
+		if wasSet {
+			os.Setenv(testKey, originalValue)
+		} else {
+			os.Unsetenv(testKey)
+		}
+	})
+
+	reader := &OSReader{}
+
+	tests := []struct {
+		name string
+		key  string
+		want string
+	}{
+		{
+			name: "existing environment variable",
+			key:  testKey,
+			want: testValue,
+		},
+		{
+			name: "non-existing environment variable",
+			key:  "NONEXISTENT_ENV_VAR_TESTING_12345",
+			want: "",
+		},
+		{
+			name: "empty key",
+			key:  "",
+			want: "",
+		},
+	}
+
+	for _, tt := range tests { //nolint:paralleltest // Test modifies environment variables
+		t.Run(tt.name, func(t *testing.T) {
+			// Cannot run in parallel because parent test modifies environment variables
+			got := reader.Getenv(tt.key)
+			if got != tt.want {
+				t.Errorf("OSReader.Getenv() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+// TestReader_InterfaceCompliance ensures OSReader implements the Reader interface
+func TestReader_InterfaceCompliance(t *testing.T) {
+	t.Parallel()
+	var _ Reader = &OSReader{}
+	// If this compiles, the test passes
+}

go.mod

@@ -1,3 +1,5 @@
 module github.com/stacklok/toolhive-core
 
 go 1.25.6
+
+require go.uber.org/mock v0.6.0

go.sum

@@ -0,0 +1,2 @@
+go.uber.org/mock v0.6.0 h1:hyF9dfmbgIX5EfOdasqLsWD6xqpNZlXblLB/Dbnwv3Y=
+go.uber.org/mock v0.6.0/go.mod h1:KiVJ4BqZJaMj4svdfmHM0AUx4NJYO8ZNpPnZn1Z+BBU=