Adds test cases for command execution.

Introduced `CaptureStdout` function to capture standard output for a given callback in tests. Added test cases for `HelloCommand`, `CryptCommand`, and `DecryptCommand` to validate their execution using captured stdout.

example/commands/decrypt_test.go

@@ -0,0 +1,28 @@
+package commands
+
+import (
+	"github.com/matzefriedrich/cobra-extensions/internal/utils"
+	"github.com/stretchr/testify/assert"
+	"testing"
+)
+
+func Test_DecryptCommand_Execute(t *testing.T) {
+
+	// Arrange
+	const expectedMessage = "Hello World"
+
+	encryptedMessage, _ := utils.CaptureStdout(t, "", func() error {
+		encryptCommand := CreateEncryptMessageCommand()
+		encryptCommand.SetArgs([]string{"--message", expectedMessage})
+		return encryptCommand.Execute()
+	})
+
+	decryptedMessage, err := utils.CaptureStdout(t, encryptedMessage, func() error {
+		decryptCommand := CreateDecryptMessageCommand()
+		return decryptCommand.Execute()
+	})
+
+	// Assert
+	assert.NoError(t, err)
+	assert.Equal(t, expectedMessage, decryptedMessage)
+}

example/commands/encrypt_test.go

@@ -0,0 +1,18 @@
+package commands
+
+import (
+	"github.com/stretchr/testify/assert"
+	"testing"
+)
+
+func Test_CryptCommand_Execute(t *testing.T) {
+
+	// Arrange
+	sut := CreateEncryptMessageCommand()
+	sut.SetArgs([]string{"--message", "Hello World"})
+	// Act
+	err := sut.Execute()
+
+	// Assert
+	assert.NoError(t, err)
+}

example/commands/hello_test.go

@@ -0,0 +1,18 @@
+package commands
+
+import (
+	"github.com/stretchr/testify/assert"
+	"testing"
+)
+
+func Test_HelloCommand_Execute(t *testing.T) {
+	// Arrange
+	sut := CreateHelloCommand()
+	sut.SetArgs([]string{"John Doe"})
+
+	// Act
+	err := sut.Execute()
+
+	// Assert
+	assert.NoError(t, err)
+}

internal/utils/capture_stdout.go

@@ -0,0 +1,58 @@
+package utils
+
+import (
+	"bytes"
+	"os"
+	"testing"
+)
+
+// CaptureStdout captures the standard output of the provided callback function.
+//
+// Parameters:
+//   - t: the testing framework instance.
+//   - in: the input string to be written to stdin.
+//   - cb: the callback function whose stdout needs to be captured.
+//
+// Returns:
+//   - The captured stdout as a string.
+func CaptureStdout(t *testing.T, in string, cb func() error) (string, error) {
+
+	originalStdin := os.Stdin
+	defer func() { os.Stdin = originalStdin }()
+
+	originalStdOut := os.Stdout
+	defer func() { os.Stdout = originalStdOut }()
+
+	stdinReader, stdinWriter, stdinPipeErr := os.Pipe()
+	if stdinPipeErr != nil {
+		t.Fatalf("failed to create pipe: %v", stdinPipeErr)
+	}
+
+	stdoutReader, stdoutWriter, stdoutPipeErr := os.Pipe()
+	if stdoutPipeErr != nil {
+		t.Fatalf("failed to create pipe: %v", stdoutPipeErr)
+	}
+
+	os.Stdin = stdinReader
+	os.Stdout = stdoutWriter
+
+	_, _ = stdinWriter.Write([]byte(in))
+	_ = stdinWriter.Close()
+
+	output := make(chan string)
+	go func() {
+		var buf bytes.Buffer
+		_, _ = buf.ReadFrom(stdoutReader)
+		output <- buf.String()
+	}()
+
+	err := cb()
+	if err != nil {
+		return "", err
+	}
+
+	_ = stdoutWriter.Close()
+
+	data := <-output
+	return data, nil
+}