command: Ensure all answers were used in command.testInputResponseMap

Remove answers from testInputResponse as they are given, and raise an
error during cleanup if any answers remain unused.

This enables tests to ensure that the expected mock answers are actually
used in a test; previously, an entire branch of code including an input
sequence could be omitted and the test(s) would not fail.

The only test that had unused answers in this map is one leftover from
legacy state migrations, a prompt that was removed in
7c93b2e5e6

internal/command/command_test.go

@@ -716,6 +716,10 @@ func testInputMap(t *testing.T, answers map[string]string) func() {
 
 	// Return the cleanup
 	return func() {
+		if len(testInputResponseMap) > 0 {
+			t.Fatalf("expected no unused answers provided to command.testInputMap, got: %v", testInputResponseMap)
+		}
+
 		test = true
 		testInputResponseMap = nil
 	}

internal/command/init_test.go

@@ -540,11 +540,6 @@ func TestInit_backendConfigFileChange(t *testing.T) {
 	defer os.RemoveAll(td)
 	defer testChdir(t, td)()
 
-	// Ask input
-	defer testInputMap(t, map[string]string{
-		"backend-migrate-to-new": "no",
-	})()
-
 	ui := new(cli.MockUi)
 	view, _ := testView(t)
 	c := &InitCommand{

internal/command/ui_input.go

@@ -90,6 +90,7 @@ func (i *UIInput) Input(ctx context.Context, opts *terraform.InputOpts) (string,
 			return "", fmt.Errorf("unexpected input request in test: %s", opts.Id)
 		}
 
+		delete(testInputResponseMap, opts.Id)
 		return v, nil
 	}