Shared Preferences Mock
Shared preferences mock is a lightweight library that lets you increase coverage of unit tests and simplify code for them with one line of code.
Motivation
Unit test on Android uses a framework mock where every method throws UnsupportedOperationException
or does nothing depending on your settings in Gradle testOptions
.
In unit tests, we mostly test business logic, which often depends on preferences. Therefore you should mock all classes which use SharedPreferences
inside. It is a lot of boilerplate in tests. Moreover, because of this limitation, we never test preferences class code. However, it also may have bugs.
Under the hood
Under the hood the library implements SharedPreferences
, Context.getSharedPreferences
and Context.deleteSharedPreferences
in memory using only Java API. Check the differences in the differences paragraph.
Download
Important: changed since 1.2.0
Add it in your root build.gradle at the end of repositories:
allprojects {
repositories {
mavenCentral()
}
}
Add the dependency:
dependencies {
// See the actual version above in the maven badge
testImplementation 'io.github.ivanshafran:shared-preferences-mock:x.y.z'
}
Enable 1.8 Java compile option if it's not enabled yet:
android {
compileOptions {
sourceCompatibility JavaVersion.VERSION_1_8
targetCompatibility JavaVersion.VERSION_1_8
}
}
Release notes
Click to see release notes
Version 1.2.4
- Master branch to main
Version 1.2.3
- First automatic release to maven central
Version 1.2.1-1.2.2
- Lost versions
Version 1.2.0
- First release to maven central
Version 1.1
- Android X support. Thanks to Neal Sanche
Version 1.0
- First release
Usage
In most cases, preference class or preference utils depends on Context
. In unit test instead of real Context
pass Context
created by new SPMockBuilder().createContext()
.
If you already have Context
with some mocked methods, you can use new SPMockBuilder().wrapContext(preconfiguredContext)
.
If you need raw SharedPreferences
use new SPMockBuilder().createSharedPreferences()
.
If thread safety is necessary for your test, then configure SPMockBuilder.setThreadSafe(true)
. It is false by default.
Sample
Full sample code in sample folder. Simplified version is below:
public class CounterPreferences {
// ...
private final SharedPreferences sharedPreferences;
public CounterPreferences(@NonNull final Context context) {
sharedPreferences = context.getSharedPreferences(FILENAME, Context.MODE_PRIVATE);
}
public int getCounter() {
return sharedPreferences.getInt(KEY, 0);
}
// ...
}
public class ShowMessageLogic {
// ...
public boolean shouldShowMessage() {
return counterPreferences.getCounter() >= 42;
}
}
public class ShowMessageLogicTest {
private final SPMockBuilder spMockBuilder = new SPMockBuilder();
private CounterPreferences counterPreferences;
private ShowMessageLogic showMessageLogic;
@Before
public void setUp() {
counterPreferences = new CounterPreferences(spMockBuilder.createContext());
showMessageLogic = new ShowMessageLogic(counterPreferences);
}
@Test
public void on42CounterItShouldShowMessage() {
counterPreferences.setCounter(42);
Assert.assertTrue(showMessageLogic.shouldShowMessage());
}
@Test
public void onLessThan42ItShouldNotShowMessage() {
counterPreferences.setCounter(41);
Assert.assertFalse(showMessageLogic.shouldShowMessage());
}
}
Alternatives
- Create
CounterPreferences
interface and implement Java version for test by yourself
- Doesn't test
CounterPreferences
implementation - Requires boilerplate code in tests
- Use Mockito
- Doesn't test
CounterPreferences
implementation
- Use Robolectric
- Has test startup delay for a few seconds
- Use instrumented test(not a unit test!)
- Requires device for testing
Differences from Android implementation
Android | Library mock | |
---|---|---|
Can be used in unit tests? | No. | Yes. |
Where it stores data? | In memory and on disk. | In memory. |
Does it have a global state? | Yes, it synchronizes via files. It is one of the main features. | No, it is better for unit tests. |
Does API synchronous? | Yes, but some methods schedule asynchronous operations. For example: apply . | All methods are synchronous and are performed immediately. |
Is it thread safe? | Yes. | No by default, because unit tests should be fast as possible for CI. You can enable it with setThreadSafety(true) in SPMockBuilder . |
Where are listeners called? | Main thread | Thread on which apply or commit are called |
Does it follow docs? | Partly no. SharedPreferencesImpl differs from docs in not the most important cases. | Library mimics SharedPreferencesImpl differences from docs. |
License
MIT License
Copyright (c) 2019 Ivan Shafran
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.