backend/local: run backend.TestBackend

This verifies that local behaves in an expected way by the backend
package.

backend/local/backend.go

@@ -127,7 +127,7 @@ func (b *Local) States() ([]string, error) {
 	// the listing always start with "default"
 	envs := []string{backend.DefaultStateName}
 
-	entries, err := ioutil.ReadDir(DefaultEnvDir)
+	entries, err := ioutil.ReadDir(b.stateEnvDir())
 	// no error if there's no envs configured
 	if os.IsNotExist(err) {
 		return envs, nil
@@ -166,7 +166,7 @@ func (b *Local) DeleteState(name string) error {
 	}
 
 	delete(b.states, name)
-	return os.RemoveAll(filepath.Join(DefaultEnvDir, name))
+	return os.RemoveAll(filepath.Join(b.stateEnvDir(), name))
 }
 
 func (b *Local) State(name string) (state.State, error) {
@@ -320,17 +320,12 @@ func (b *Local) StatePaths(name string) (string, string, string) {
 		name = backend.DefaultStateName
 	}
 
-	envDir := DefaultEnvDir
-	if b.StateEnvDir != "" {
-		envDir = b.StateEnvDir
-	}
-
 	if name == backend.DefaultStateName {
 		if statePath == "" {
 			statePath = DefaultStateFilename
 		}
 	} else {
-		statePath = filepath.Join(envDir, name, DefaultStateFilename)
+		statePath = filepath.Join(b.stateEnvDir(), name, DefaultStateFilename)
 	}
 
 	if stateOutPath == "" {
@@ -353,12 +348,7 @@ func (b *Local) createState(name string) error {
 		return nil
 	}
 
-	envDir := DefaultEnvDir
-	if b.StateEnvDir != "" {
-		envDir = b.StateEnvDir
-	}
-
-	stateDir := filepath.Join(envDir, name)
+	stateDir := filepath.Join(b.stateEnvDir(), name)
 	s, err := os.Stat(stateDir)
 	if err == nil && s.IsDir() {
 		// no need to check for os.IsNotExist, since that is covered by os.MkdirAll
@@ -374,6 +364,15 @@ func (b *Local) createState(name string) error {
 	return nil
 }
 
+// stateEnvDir returns the directory where state environments are stored.
+func (b *Local) stateEnvDir() string {
+	if b.StateEnvDir != "" {
+		return b.StateEnvDir
+	}
+
+	return DefaultEnvDir
+}
+
 // currentStateName returns the name of the current named state as set in the
 // configuration files.
 // If there are no configured environments, currentStateName returns "default"

backend/local/backend_test.go

@@ -20,6 +20,10 @@ func TestLocal_impl(t *testing.T) {
 	var _ backend.CLI = new(Local)
 }
 
+func TestLocal_backend(t *testing.T) {
+	backend.TestBackend(t, TestLocal(t))
+}
+
 func checkState(t *testing.T, path, expected string) {
 	// Read the state
 	f, err := os.Open(path)

backend/local/testing.go

@@ -21,6 +21,7 @@ func TestLocal(t *testing.T) *Local {
 		StatePath:       filepath.Join(tempDir, "state.tfstate"),
 		StateOutPath:    filepath.Join(tempDir, "state.tfstate"),
 		StateBackupPath: filepath.Join(tempDir, "state.tfstate.bak"),
+		StateEnvDir:     filepath.Join(tempDir, "state.tfstate.d"),
 		ContextOpts:     &terraform.ContextOpts{},
 	}
 }

backend/testing.go

@@ -82,6 +82,10 @@ func testBackendStates(t *testing.T, b Backend) {
 	// Verify they are distinct states
 	{
 		s := barState.State()
+		if s == nil {
+			s = terraform.NewState()
+		}
+
 		s.Lineage = "bar"
 		if err := barState.WriteState(s); err != nil {
 			t.Fatalf("bad: %s", err)
@@ -93,7 +97,7 @@ func testBackendStates(t *testing.T, b Backend) {
 		if err := fooState.RefreshState(); err != nil {
 			t.Fatalf("bad: %s", err)
 		}
-		if v := fooState.State(); v.Lineage == "bar" {
+		if v := fooState.State(); v != nil && v.Lineage == "bar" {
 			t.Fatalf("bad: %#v", v)
 		}
 	}