test(key): add unit tests for key behavior

internal/key/key.go

@@ -5,6 +5,7 @@ import (
 	"crypto/rsa"
 	"crypto/x509"
 	"encoding/pem"
+	"io"
 	"log"
 	"os"
 	"path/filepath"
@@ -12,6 +13,18 @@ import (
 	"golang.org/x/crypto/ssh"
 )
 
+var (
+	rsaGenerateKey  = rsa.GenerateKey
+	pemEncode       = pem.Encode
+	sshNewPublicKey = func(key interface{}) (ssh.PublicKey, error) {
+		return ssh.NewPublicKey(key)
+	}
+	pubKeyWrite = func(w io.Writer, data []byte) (int, error) {
+		return w.Write(data)
+	}
+	osOpenFile = os.OpenFile
+)
+
 func GenerateSSHKeyIfNotExist(keyPath string) error {
 	if _, err := os.Stat(keyPath); err == nil {
 		log.Printf("SSH key already exists at %s", keyPath)
@@ -20,7 +33,7 @@ func GenerateSSHKeyIfNotExist(keyPath string) error {
 
 	log.Printf("SSH key not found at %s, generating new key pair...", keyPath)
 
-	privateKey, err := rsa.GenerateKey(rand.Reader, 4096)
+	privateKey, err := rsaGenerateKey(rand.Reader, 4096)
 	if err != nil {
 		return err
 	}
@@ -35,29 +48,29 @@ func GenerateSSHKeyIfNotExist(keyPath string) error {
 		return err
 	}
 
-	privateKeyFile, err := os.OpenFile(keyPath, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0600)
+	privateKeyFile, err := osOpenFile(keyPath, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0600)
 	if err != nil {
 		return err
 	}
 	defer privateKeyFile.Close()
 
-	if err := pem.Encode(privateKeyFile, privateKeyPEM); err != nil {
+	if err := pemEncode(privateKeyFile, privateKeyPEM); err != nil {
 		return err
 	}
 
-	publicKey, err := ssh.NewPublicKey(&privateKey.PublicKey)
+	publicKey, err := sshNewPublicKey(&privateKey.PublicKey)
 	if err != nil {
 		return err
 	}
 
 	pubKeyPath := keyPath + ".pub"
-	pubKeyFile, err := os.OpenFile(pubKeyPath, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0644)
+	pubKeyFile, err := osOpenFile(pubKeyPath, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0644)
 	if err != nil {
 		return err
 	}
 	defer pubKeyFile.Close()
 
-	_, err = pubKeyFile.Write(ssh.MarshalAuthorizedKey(publicKey))
+	_, err = pubKeyWrite(pubKeyFile, ssh.MarshalAuthorizedKey(publicKey))
 	if err != nil {
 		return err
 	}

internal/key/key_test.go

@@ -0,0 +1,235 @@
+package key
+
+import (
+	"crypto/rsa"
+	"encoding/pem"
+	"errors"
+	"io"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"golang.org/x/crypto/ssh"
+)
+
+func TestGenerateSSHKeyIfNotExist(t *testing.T) {
+	tempDir := t.TempDir()
+
+	tests := []struct {
+		name      string
+		setup     func(t *testing.T, tempDir string) string
+		mockSetup func() func()
+		wantErr   bool
+		errStr    string
+		verify    func(t *testing.T, keyPath string)
+	}{
+		{
+			name: "GenerateNewKey",
+			setup: func(t *testing.T, tempDir string) string {
+				return filepath.Join(tempDir, "id_rsa")
+			},
+			verify: func(t *testing.T, keyPath string) {
+				pubKeyPath := keyPath + ".pub"
+				if _, err := os.Stat(keyPath); os.IsNotExist(err) {
+					t.Errorf("Private key file not created")
+				}
+				if _, err := os.Stat(pubKeyPath); os.IsNotExist(err) {
+					t.Errorf("Public key file not created")
+				}
+				privateKeyBytes, err := os.ReadFile(keyPath)
+				if err != nil {
+					t.Fatalf("Failed to read private key: %v", err)
+				}
+				if _, err = ssh.ParseRawPrivateKey(privateKeyBytes); err != nil {
+					t.Errorf("Failed to parse private key: %v", err)
+				}
+				publicKeyBytes, err := os.ReadFile(pubKeyPath)
+				if err != nil {
+					t.Fatalf("Failed to read public key: %v", err)
+				}
+				if _, _, _, _, err = ssh.ParseAuthorizedKey(publicKeyBytes); err != nil {
+					t.Errorf("Failed to parse public key: %v", err)
+				}
+			},
+		},
+		{
+			name: "DoNotOverwriteExistingKey",
+			setup: func(t *testing.T, tempDir string) string {
+				keyPath := filepath.Join(tempDir, "existing_id_rsa")
+				dummyPrivate := "dummy private"
+				dummyPublic := "dummy public"
+				if err := os.WriteFile(keyPath, []byte(dummyPrivate), 0600); err != nil {
+					t.Fatalf("Failed to create dummy private key: %v", err)
+				}
+				if err := os.WriteFile(keyPath+".pub", []byte(dummyPublic), 0644); err != nil {
+					t.Fatalf("Failed to create dummy public key: %v", err)
+				}
+				return keyPath
+			},
+			verify: func(t *testing.T, keyPath string) {
+				gotPrivate, _ := os.ReadFile(keyPath)
+				if string(gotPrivate) != "dummy private" {
+					t.Errorf("Private key was overwritten")
+				}
+				gotPublic, _ := os.ReadFile(keyPath + ".pub")
+				if string(gotPublic) != "dummy public" {
+					t.Errorf("Public key was overwritten")
+				}
+			},
+		},
+		{
+			name: "CreateNestedDirectories",
+			setup: func(t *testing.T, tempDir string) string {
+				return filepath.Join(tempDir, "nested", "dir", "id_rsa")
+			},
+			verify: func(t *testing.T, keyPath string) {
+				if _, err := os.Stat(keyPath); os.IsNotExist(err) {
+					t.Errorf("Private key file not created in nested directory")
+				}
+			},
+		},
+		{
+			name: "FailureMkdirAll",
+			setup: func(t *testing.T, tempDir string) string {
+				dirPath := filepath.Join(tempDir, "file_as_dir")
+				if err := os.WriteFile(dirPath, []byte("not a dir"), 0644); err != nil {
+					t.Fatalf("Failed to create file: %v", err)
+				}
+				return filepath.Join(dirPath, "id_rsa")
+			},
+			wantErr: true,
+		},
+		{
+			name: "PrivateExistsPublicMissing",
+			setup: func(t *testing.T, tempDir string) string {
+				keyPath := filepath.Join(tempDir, "partial_id_rsa")
+				if err := os.WriteFile(keyPath, []byte("private"), 0600); err != nil {
+					t.Fatalf("Failed to create private key: %v", err)
+				}
+				return keyPath
+			},
+			verify: func(t *testing.T, keyPath string) {
+				if _, err := os.Stat(keyPath + ".pub"); !os.IsNotExist(err) {
+					t.Errorf("Public key should NOT have been created if private key existed")
+				}
+			},
+		},
+		{
+			name: "FailureRSAGenerateKey",
+			setup: func(t *testing.T, tempDir string) string {
+				return filepath.Join(tempDir, "fail_rsa")
+			},
+			mockSetup: func() func() {
+				old := rsaGenerateKey
+				rsaGenerateKey = func(random io.Reader, bits int) (*rsa.PrivateKey, error) {
+					return nil, errors.New("rsa error")
+				}
+				return func() { rsaGenerateKey = old }
+			},
+			wantErr: true,
+			errStr:  "rsa error",
+		},
+		{
+			name: "FailureOpenFilePrivate",
+			setup: func(t *testing.T, tempDir string) string {
+				return filepath.Join(tempDir, "fail_open_private")
+			},
+			mockSetup: func() func() {
+				old := osOpenFile
+				osOpenFile = func(name string, flag int, perm os.FileMode) (*os.File, error) {
+					return nil, errors.New("open error")
+				}
+				return func() { osOpenFile = old }
+			},
+			wantErr: true,
+			errStr:  "open error",
+		},
+		{
+			name: "FailurePemEncode",
+			setup: func(t *testing.T, tempDir string) string {
+				return filepath.Join(tempDir, "fail_pem")
+			},
+			mockSetup: func() func() {
+				old := pemEncode
+				pemEncode = func(out io.Writer, b *pem.Block) error {
+					return errors.New("pem error")
+				}
+				return func() { pemEncode = old }
+			},
+			wantErr: true,
+			errStr:  "pem error",
+		},
+		{
+			name: "FailureSSHNewPublicKey",
+			setup: func(t *testing.T, tempDir string) string {
+				return filepath.Join(tempDir, "fail_ssh")
+			},
+			mockSetup: func() func() {
+				old := sshNewPublicKey
+				sshNewPublicKey = func(key interface{}) (ssh.PublicKey, error) {
+					return nil, errors.New("ssh error")
+				}
+				return func() { sshNewPublicKey = old }
+			},
+			wantErr: true,
+			errStr:  "ssh error",
+		},
+		{
+			name: "FailureOpenFilePublic",
+			setup: func(t *testing.T, tempDir string) string {
+				return filepath.Join(tempDir, "fail_open_public")
+			},
+			mockSetup: func() func() {
+				old := osOpenFile
+				osOpenFile = func(name string, flag int, perm os.FileMode) (*os.File, error) {
+					if filepath.Ext(name) == ".pub" {
+						return nil, errors.New("open pub error")
+					}
+					return os.OpenFile(name, flag, perm)
+				}
+				return func() { osOpenFile = old }
+			},
+			wantErr: true,
+			errStr:  "open pub error",
+		},
+		{
+			name: "FailurePubKeyWrite",
+			setup: func(t *testing.T, tempDir string) string {
+				return filepath.Join(tempDir, "fail_write")
+			},
+			mockSetup: func() func() {
+				old := pubKeyWrite
+				pubKeyWrite = func(w io.Writer, data []byte) (int, error) {
+					return 0, errors.New("write error")
+				}
+				return func() { pubKeyWrite = old }
+			},
+			wantErr: true,
+			errStr:  "write error",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			keyPath := tt.setup(t, tempDir)
+			if tt.mockSetup != nil {
+				cleanup := tt.mockSetup()
+				defer cleanup()
+			}
+
+			err := GenerateSSHKeyIfNotExist(keyPath)
+
+			if (err != nil) != tt.wantErr {
+				t.Errorf("GenerateSSHKeyIfNotExist() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			if tt.wantErr && tt.errStr != "" && err != nil && err.Error() != tt.errStr {
+				t.Errorf("GenerateSSHKeyIfNotExist() error = %v, wantErrStr %v", err, tt.errStr)
+			}
+
+			if tt.verify != nil {
+				tt.verify(t, keyPath)
+			}
+		})
+	}
+}