This document discusses improving testability of Android applications by reducing coupling between components. It presents an example of an Android MapActivity that is tightly coupled to MapFragment and Toast, making it difficult to test. The document then introduces an OnPermissionResultListener class that receives permission results and calls methods on a PermittedView interface, decoupling the logic from specific views and allowing it to be more easily tested. This improves testability by removing direct dependencies between classes.

1. If Android Tests
Could Talk
Matt Dupree

2. Their pace has quickened

3. This code is garbage

4. –Steve Freeman and Nat Pryce, Growing Object Oriented Software Guided
by Tests
“for a class to be easy to unit-test, the class
must…be loosely coupled and highly cohesive
—in other words, well-designed.”

5. –Steve Freeman and Nat Pryce, Growing Object Oriented Software Guided
by Tests
“for a class to be easy to unit-test, the class
must…be loosely coupled and highly cohesive
—in other words, well-designed.”

6. –Steve Freeman and Nat Pryce, Growing Object Oriented Software Guided
by Tests
“for a class to be easy to unit-test, the class
must…be loosely coupled and highly cohesive
—in other words, well-designed.”

7. Activities tend to have tight
coupling and poor cohesion

8. Application components (activities,
services, providers, receivers) are interfaces
for your application to interact with the
operating system; don’t take them as a
recommendation of the facilities you
should architect your entire application
around.
—Chet Haase, Developing for Android VII

9. Activities tend to have tight
coupling and poor cohesion

11. @Override
public void onRequestPermissionsResult(final int requestCode,
@NonNull final String[] permissions,
@NonNull final int[] grantResults) {
if (requestCode != REQUEST_LOCATION_PERMISSION) {
return;
}
if (permissions.length == 1 &&
LOCATION_PERMISSION.equals(permissions[0]) &&
grantResults[0] == PackageManager.PERMISSION_GRANTED) {
// Permission has been granted.
if (mMapFragment != null) {
mMapFragment.setMyLocationEnabled(true);
}
} else {
// Permission was denied. Display error message.
Toast.makeText(this, R.string.map_permission_denied,
Toast.LENGTH_SHORT).show();
}
super.onRequestPermissionsResult(requestCode, permissions,
grantResults);
}

12. @Override
public void onRequestPermissionsResult(final int requestCode,
@NonNull final String[] permissions,
@NonNull final int[] grantResults) {
if (requestCode != REQUEST_LOCATION_PERMISSION) {
return;
}
if (permissions.length == 1 &&
LOCATION_PERMISSION.equals(permissions[0]) &&
grantResults[0] == PackageManager.PERMISSION_GRANTED) {
// Permission has been granted.
if (mMapFragment != null) {
mMapFragment.setMyLocationEnabled(true);
}
} else {
// Permission was denied. Display error message.
Toast.makeText(this, R.string.map_permission_denied,
Toast.LENGTH_SHORT).show();
}
super.onRequestPermissionsResult(requestCode, permissions,
grantResults);
}

13. @Override
public void onRequestPermissionsResult(final int requestCode,
@NonNull final String[] permissions,
@NonNull final int[] grantResults) {
if (requestCode != REQUEST_LOCATION_PERMISSION) {
return;
}
if (permissions.length == 1 &&
LOCATION_PERMISSION.equals(permissions[0]) &&
grantResults[0] == PackageManager.PERMISSION_GRANTED) {
// Permission has been granted.
if (mMapFragment != null) {
mMapFragment.setMyLocationEnabled(true);
}
} else {
// Permission was denied. Display error message.
Toast.makeText(this, R.string.map_permission_denied,
Toast.LENGTH_SHORT).show();
}
super.onRequestPermissionsResult(requestCode, permissions,
grantResults);
}

14. @Override
public void onRequestPermissionsResult(final int requestCode,
@NonNull final String[] permissions,
@NonNull final int[] grantResults) {
if (requestCode != REQUEST_LOCATION_PERMISSION) {
return;
}
if (permissions.length == 1 &&
LOCATION_PERMISSION.equals(permissions[0]) &&
grantResults[0] == PackageManager.PERMISSION_GRANTED) {
// Permission has been granted.
if (mMapFragment != null) {
mMapFragment.setMyLocationEnabled(true);
}
} else {
// Permission was denied. Display error message.
Toast.makeText(this, R.string.map_permission_denied,
Toast.LENGTH_SHORT).show();
}
super.onRequestPermissionsResult(requestCode, permissions,
grantResults);
}

15. @Override
public void onRequestPermissionsResult(final int requestCode,
@NonNull final String[] permissions,
@NonNull final int[] grantResults) {
if (requestCode != REQUEST_LOCATION_PERMISSION) {
return;
}
if (permissions.length == 1 &&
LOCATION_PERMISSION.equals(permissions[0]) &&
grantResults[0] == PackageManager.PERMISSION_GRANTED) {
// Permission has been granted.
if (mMapFragment != null) {
mMapFragment.setMyLocationEnabled(true);
}
} else {
// Permission was denied. Display error message.
Toast.makeText(this, R.string.map_permission_denied,
Toast.LENGTH_SHORT).show();
}
super.onRequestPermissionsResult(requestCode, permissions,
grantResults);
}

17. @Test
public void showsToastIfPermissionIsRejected()
throws Exception {
MapActivity mapActivity = new MapActivity();
mapActivity.onRequestPermissionsResult(
MapActivity.REQUEST_LOCATION_PERMISSION,
new String[]{MapActivity.LOCATION_PERMISSION}, new int[]{
PackageManager.PERMISSION_DENIED});
assertToastDisplayed();
}

18. @Test
public void showsToastIfPermissionIsRejected()
throws Exception {
MapActivity mapActivity = new MapActivity();
mapActivity.onRequestPermissionsResult(
MapActivity.REQUEST_LOCATION_PERMISSION,
new String[]{MapActivity.LOCATION_PERMISSION}, new int[]{
PackageManager.PERMISSION_DENIED});
assertToastDisplayed();
}

19. @Test
public void showsToastIfPermissionIsRejected()
throws Exception {
MapActivity mapActivity = new MapActivity();
mapActivity.onRequestPermissionsResult(
MapActivity.REQUEST_LOCATION_PERMISSION,
new String[]{MapActivity.LOCATION_PERMISSION}, new int[]{
PackageManager.PERMISSION_DENIED});
assertToastDisplayed();
}

20. @Test
public void showsToastIfPermissionIsRejected()
throws Exception {
MapActivity mapActivity = new MapActivity();
mapActivity.onRequestPermissionsResult(
MapActivity.REQUEST_LOCATION_PERMISSION,
new String[]{MapActivity.LOCATION_PERMISSION}, new int[]{
PackageManager.PERMISSION_DENIED});
assertToastDisplayed();
}

21. private void assertToastDisplayed() {
// It can't be done, sir
}

22. @Override
public void onRequestPermissionsResult(final int requestCode,
@NonNull final String[] permissions,
@NonNull final int[] grantResults) {
if (requestCode != REQUEST_LOCATION_PERMISSION) {
return;
}
if (permissions.length == 1 &&
LOCATION_PERMISSION.equals(permissions[0]) &&
grantResults[0] == PackageManager.PERMISSION_GRANTED) {
// Permission has been granted.
if (mMapFragment != null) {
mMapFragment.setMyLocationEnabled(true);
}
} else {
// Permission was denied. Display error message.
Toast.makeText(this, R.string.map_permission_denied,
Toast.LENGTH_SHORT).show();
}
super.onRequestPermissionsResult(requestCode, permissions,
grantResults);
}

27. MapActivity is tightly coupled
with MapFragment and Toast

28. static class OnPermissionResultListener {
private final PermittedView mPermittedView;
void onPermissionResult(final int requestCode,
final String[] permissions, final int[] grantResults) {}
interface PermittedView {
void displayPermissionDenied();
void displayPermittedView();
}
}

29. static class OnPermissionResultListener {
private final PermittedView mPermittedView;
void onPermissionResult(final int requestCode,
final String[] permissions, final int[] grantResults) {}
interface PermittedView {
void displayPermissionDenied();
void displayPermittedView();
}
}

30. static class OnPermissionResultListener {
private final PermittedView mPermittedView;
void onPermissionResult(final int requestCode,
final String[] permissions, final int[] grantResults) {}
interface PermittedView {
void displayPermissionDenied();
void displayPermittedView();
}
}

31. void onPermissionResult(final int requestCode,
final String[] permissions, final int[] grantResults) {
if (requestCode != MapActivity.REQUEST_LOCATION_PERMISSION) {
return;
}
if (permissions.length == 1 &&
MapActivity.LOCATION_PERMISSION.equals(permissions[0]) &&
grantResults[0] == PackageManager.PERMISSION_GRANTED) {
// Permission has been granted.
mPermittedView.displayPermittedView();
} else {
// Permission was denied. Display error message.
mPermittedView.displayPermissionDenied();
}
}

32. void onPermissionResult(final int requestCode,
final String[] permissions, final int[] grantResults) {
if (requestCode != MapActivity.REQUEST_LOCATION_PERMISSION) {
return;
}
if (permissions.length == 1 &&
MapActivity.LOCATION_PERMISSION.equals(permissions[0]) &&
grantResults[0] == PackageManager.PERMISSION_GRANTED) {
// Permission has been granted.
mPermittedView.displayPermittedView();
} else {
// Permission was denied. Display error message.
mPermittedView.displayPermissionDenied();
}
}

33. @Test
public void displaysErrorWhenPermissionRejected() throws Exception {
OnPermissionResultListener onPermissionResultListener =
new OnPermissionResultListener(mPermittedView);
onPermissionResultListener.onPermissionResult(
MapActivity.REQUEST_LOCATION_PERMISSION,
new String[]{MapActivity.LOCATION_PERMISSION},
new int[]{PackageManager.PERMISSION_DENIED});
verify(mPermittedView).displayPermissionDenied();
}

34. @Test
public void displaysErrorWhenPermissionRejected() throws Exception {
OnPermissionResultListener onPermissionResultListener =
new OnPermissionResultListener(mPermittedView);
onPermissionResultListener.onPermissionResult(
MapActivity.REQUEST_LOCATION_PERMISSION,
new String[]{MapActivity.LOCATION_PERMISSION},
new int[]{PackageManager.PERMISSION_DENIED});
verify(mPermittedView).displayPermissionDenied();
}

35. @Test
public void displaysErrorWhenPermissionRejected() throws Exception {
OnPermissionResultListener onPermissionResultListener =
new OnPermissionResultListener(mPermittedView);
onPermissionResultListener.onPermissionResult(
MapActivity.REQUEST_LOCATION_PERMISSION,
new String[]{MapActivity.LOCATION_PERMISSION},
new int[]{PackageManager.PERMISSION_DENIED});
verify(mPermittedView).displayPermissionDenied();
}

36. @Test
public void displaysErrorWhenPermissionRejected() throws Exception {
OnPermissionResultListener onPermissionResultListener =
new OnPermissionResultListener(mPermittedView);
onPermissionResultListener.onPermissionResult(
MapActivity.REQUEST_LOCATION_PERMISSION,
new String[]{MapActivity.LOCATION_PERMISSION},
new int[]{PackageManager.PERMISSION_DENIED});
verify(mPermittedView).displayPermissionDenied();
}

37. Who cares?

38. –Edward Yourdon and Larry Constantine
“what we are striving for is loosely coupled
systems…in which one can study (or debug, or
maintain) any one module without having to
know very much about any other modules in the
system”

40. @Override
public void displayPermissionDenied() {
Toast.makeText(MapActivity.this, R.string.map_permission_denied,
Toast.LENGTH_SHORT).show();
}

41. @Override
public void displayPermissionDenied() {
PermissionsUtils.displayConditionalPermissionDenialSnackbar(this,
R.string.map_permission_denied, PERMISSIONS,
REQUEST_LOCATION_PERMISSION, false);
}

42. –Kent Beck, TDD By Example
“Dependency is the key problem in software
development at all scales…if dependency is the
problem, duplication is the symptom.”

44. @Override
public void onRequestPermissionsResult(final int requestCode,
@NonNull final String[] permissions,
@NonNull final int[] grantResults) {
if (grantResults.length == APP_REQUIRED_PERMISSIONS.length &&
grantResults[0] == PackageManager.PERMISSION_GRANTED &&
grantResults[1] == PackageManager.PERMISSION_GRANTED) {
// If permission granted then refresh account list so user can
// select an account.
clearSnackbar();
reloadAccounts();
refreshAccountListUI();
} else {
LOGI(TAG, "onRequestPermissionResult with permissions
denied");
mSnackbar = new WeakReference<>(PermissionsUtils
.displayConditionalPermissionDenialSnackbar(
getActivity(),
R.string.welcome_permissions_rationale,
APP_REQUIRED_PERMISSIONS,
REQUEST_PERMISSION_REQUEST_CODE));
}
}

45. Activities tend to have tight
coupling and poor cohesion

46. –Steve Freeman and Nat Pryce, Growing Object Oriented Software Guided
by Tests
“for a class to be easy to unit-test, the class
must…be loosely coupled and highly cohesive
—in other words, well-designed.”

47. Activities tend to have tight
coupling and poor cohesion

48. –Steve Freeman and Nat Pryce, Growing Object Oriented Software Guided
by Tests
“for a class to be easy to unit-test, the class
must…be loosely coupled and highly cohesive
—in other words, well-designed.”

50. private void displaySessionData(final SessionDetailModel data) {
//46 statement method inside a 900 line class
// Handle Keynote as a special case, where the user cannot remove it
// from the schedule (it is auto added to schedule on sync)
mShowFab = (AccountUtils.hasActiveAccount(getContext()) &&
!data.isKeynote());
mAddScheduleFab
.setVisibility(mShowFab ? View.VISIBLE : View.INVISIBLE);
if (!data.isKeynote()) {
showInScheduleDeferred(data.isInSchedule());
}
//...
updateTimeBasedUi(data);
}

51. private void displaySessionData(final SessionDetailModel data) {
//46 statement method inside a 900 line class!
// Handle Keynote as a special case, where the user cannot remove it
// from the schedule (it is auto added to schedule on sync)
mShowFab = (AccountUtils.hasActiveAccount(getContext()) &&
!data.isKeynote());
mAddScheduleFab
.setVisibility(mShowFab ? View.VISIBLE : View.INVISIBLE);
if (!data.isKeynote()) {
showInScheduleDeferred(data.isInSchedule());
}
//...
updateTimeBasedUi(data);
}

52. private void displaySessionData(final SessionDetailModel data) {
//46 statement method inside a 900 line class
// Handle Keynote as a special case, where the user cannot remove it
// from the schedule (it is auto added to schedule on sync)
mShowFab = (AccountUtils.hasActiveAccount(getContext()) &&
!data.isKeynote());
mAddScheduleFab
.setVisibility(mShowFab ? View.VISIBLE : View.INVISIBLE);
if (!data.isKeynote()) {
showInScheduleDeferred(data.isInSchedule());
}
//...
updateTimeBasedUi(data);
}

53. private void displaySessionData(final SessionDetailModel data) {
//46 statement method inside a 900 line class
// Handle Keynote as a special case, where the user cannot remove it
// from the schedule (it is auto added to schedule on sync)
mShowFab = (AccountUtils.hasActiveAccount(getContext()) &&
!data.isKeynote());
mAddScheduleFab
.setVisibility(mShowFab ? View.VISIBLE : View.INVISIBLE);
if (!data.isKeynote()) {
showInScheduleDeferred(data.isInSchedule());
}
//...
updateTimeBasedUi(data);
}

54. private void displaySessionData(final SessionDetailModel data) {
//46 statement method inside a 900 line class
// Handle Keynote as a special case, where the user cannot remove it
// from the schedule (it is auto added to schedule on sync)
mShowFab = (AccountUtils.hasActiveAccount(getContext()) &&
!data.isKeynote());
mAddScheduleFab
.setVisibility(mShowFab ? View.VISIBLE : View.INVISIBLE);
if (!data.isKeynote()) {
showInScheduleDeferred(data.isInSchedule());
}
//...
updateTimeBasedUi(data);
}

56. @Test
public void onlyProvidesAddSessionToggleIfSessionIsNotKeynote()
throws Exception {
SessionDetailFragment sessionDetailFragment =
new SessionDetailFragment();
final SessionDetailModel sessionDetailModel =
mock(SessionDetailModel.class);
when(sessionDetailModel.isKeynote()).thenReturn(false);
sessionDetailFragment.displayData(sessionDetailModel,
SessionDetailModel.SessionDetailQueryEnum.SESSIONS);
final View addScheduleButton =
sessionDetailFragment.getView()
.findViewById(R.id.add_schedule_button);
assertTrue(addScheduleButton.getVisibility() == View.INVISIBLE);
}

57. @Test
public void onlyProvidesAddSessionToggleIfSessionIsNotKeynote()
throws Exception {
SessionDetailFragment sessionDetailFragment =
new SessionDetailFragment();
final SessionDetailModel sessionDetailModel =
mock(SessionDetailModel.class);
when(sessionDetailModel.isKeynote()).thenReturn(false);
sessionDetailFragment.displayData(sessionDetailModel,
SessionDetailModel.SessionDetailQueryEnum.SESSIONS);
final View addScheduleButton =
sessionDetailFragment.getView()
.findViewById(R.id.add_schedule_button);
assertTrue(addScheduleButton.getVisibility() == View.INVISIBLE);
}

58. @Test
public void onlyProvidesAddSessionToggleIfSessionIsNotKeynote()
throws Exception {
SessionDetailFragment sessionDetailFragment =
new SessionDetailFragment();
final SessionDetailModel sessionDetailModel =
mock(SessionDetailModel.class);
when(sessionDetailModel.isKeynote()).thenReturn(false);
sessionDetailFragment.displayData(sessionDetailModel,
SessionDetailModel.SessionDetailQueryEnum.SESSIONS);
final View addScheduleButton =
sessionDetailFragment.getView()
.findViewById(R.id.add_schedule_button);
assertTrue(addScheduleButton.getVisibility() == View.INVISIBLE);
}

59. @Test
public void onlyProvidesAddSessionToggleIfSessionIsNotKeynote()
throws Exception {
SessionDetailFragment sessionDetailFragment =
new SessionDetailFragment();
final SessionDetailModel sessionDetailModel =
mock(SessionDetailModel.class);
when(sessionDetailModel.isKeynote()).thenReturn(false);
sessionDetailFragment.displayData(sessionDetailModel,
SessionDetailModel.SessionDetailQueryEnum.SESSIONS);
final View addScheduleButton =
sessionDetailFragment.getView()
.findViewById(R.id.add_schedule_button);
assertTrue(addScheduleButton.getVisibility() == View.INVISIBLE);
}

61. @Test
public void onlyProvidesAddSessionToggleIfSessionIsNotKeynote()
throws Exception {
SessionDetailFragment sessionDetailFragment =
new SessionDetailFragment();
final SessionDetailModel sessionDetailModel =
mock(SessionDetailModel.class);
when(sessionDetailModel.isKeynote()).thenReturn(false);
sessionDetailFragment.onActivityCreated(null);
sessionDetailFragment.displayData(sessionDetailModel,
SessionDetailModel.SessionDetailQueryEnum.SESSIONS);
final View addScheduleButton =
sessionDetailFragment.getView()
.findViewById(R.id.add_schedule_button);
assertTrue(addScheduleButton.getVisibility() == View.INVISIBLE);
}

62. @Test
public void onlyProvidesAddSessionToggleIfSessionIsNotKeynote()
throws Exception {
SessionDetailFragment sessionDetailFragment =
new SessionDetailFragment();
final SessionDetailModel sessionDetailModel =
mock(SessionDetailModel.class);
when(sessionDetailModel.isKeynote()).thenReturn(false);
sessionDetailFragment.onActivityCreated(null);
sessionDetailFragment.onAttach(null);
sessionDetailFragment.displayData(sessionDetailModel,
SessionDetailModel.SessionDetailQueryEnum.SESSIONS);
final View addScheduleButton =
sessionDetailFragment.getView()
.findViewById(R.id.add_schedule_button);
assertTrue(addScheduleButton.getVisibility() == View.INVISIBLE);
}

63. SessionDetailFragment
has low cohesion

64. TDD Live

65. –Steve Freeman and Nat Pryce, Growing Object Oriented Software Guided
by Tests
“for a class to be easy to unit-test, the class
must…be loosely coupled and highly cohesive
—in other words, well-designed.”

66. Activities tend to have tight
coupling and poor cohesion

67. This code is garbage

68. If Android Tests
Could Talk
https://twitter.com/philosohacker
https://twitter.com/unikeytech