Let see the code that needs to be tested:
public class DemoCodeCoverage {
public void showDemo(LibraryCode library) {
System.out.println("Hello World!");
library.runDemoApplication();
// Extract the below code to a method since LibraryCode is not passed
// Then ignore running that method
// LibraryCode library = new LibraryCode()
// library.runDemoApplication_1();
// library.runDemoApplication_2();
// library.runDemoApplication_3();
System.out.println("World ends here!");
}
public boolean showBranchingDemo(boolean signal) {
if (signal) {
signalShown();
} else {
noSignal();
}
return signal;
}
public void signalShown() {
System.out.println("signalShown!");
}
public void noSignal() {
System.out.println("NoSignal!");
}
}
public class LibraryCode {
// Library can be AWS/Database code which needs authentication
// And this authentication is not a concern for our UT
// Still will end up execption when we do our UT
public void runDemoApplication() {
throw new RuntimeException();
}
}
Below can give good code coverage:
public class DemoCodeCoverageTest {
@Test
public void testShowDemo() {
DemoCodeCoverage t = Mockito.spy(new DemoCodeCoverage());
LibraryCode lib = Mockito.mock(LibraryCode.class);
Mockito.doNothing().when(lib).runDemoApplication();
t.showDemo(lib);
// when(bloMock.doSomeStuff()).thenReturn(1);
// doReturn(1).when(bloMock).doSomeStuff();
}
@Test
public void testShowBranchingDemo() {
DemoCodeCoverage t = Mockito.spy(new DemoCodeCoverage());
assertEquals(true, t.showBranchingDemo(true));
assertEquals(false, t.showBranchingDemo(false));
}
@Test
public void testSignalShown() {
DemoCodeCoverage t = Mockito.spy(new DemoCodeCoverage());
t.showBranchingDemo(true);
Mockito.verify(t, times(1)).signalShown();
}
@Test
public void testNoSignal() {
DemoCodeCoverage t = Mockito.spy(new DemoCodeCoverage());
t.showBranchingDemo(false);
Mockito.verify(t, times(1)).noSignal();
}
}
Below are the steps to increase the test code coverage:
Case_1: Testing void method
Assume you have method the does not take any params and return nothing.
public void printHelloWorld() {
System.out.println("Hello World")
}
Still you can write test that calls this method and returns successfully without any runtimeException.
Actually we haven't tested anything here other than giving a option to run the code by our tests. Thus increase the code coverage.
Additionally you can verify the invocation:
Mockito.verify(instance, times(1)).printHelloWorld();
There are circumstances you cannot test those, example say it is third party library call, then the library might have tested already, we just need to run through it.
@Test
public void testPrintHelloWorld() {
// may be hibernate call/other 3rd party method call
instance.printHelloWorld();
}
If your tool is not strict for 100% code coverage, you can even ignore it and justify it.
Case_2: Testing a method with object created and called another method inside the testing method
Assume you have method the does call DB to add entry in Hello_World table also prints it in console like below.
public void printHelloWorld() throws DBException {
DBConnection db = new DBConnection();
db.createEntry(TABLE_NAME, "Hello World");
System.out.println("Hello World")
}
You can extract those db code into new method, then test it separately.
public void printHelloWorld() throws DBException {
makeHelloWorldEntryInTable();
System.out.println("Hello World")
}
public void makeHelloWorldEntryInTable() throws DBException {
DBConnection db = new DBConnection();
db.createEntry(TABLE_NAME, "Hello World");
}
While testing with DB you would expect the DBConnectionException as it is just unit test. So one test with @Test(expected=DBException) for makeHelloWorldEntryInTable, and another test on printHelloWorld() with skipping the method makeHelloWorldEntryInTable call like below. Thus increases the code coverage.
@Test(expected=DBException)
public void testMakeHelloWorldEntryInTable() {
//This can any third party library which cannot be configured for ut.
//One example is testing the AWS bucket exist or not.
instance.makeHelloWorldEntryInTable();
}
@Test
public void testPrintHelloWorld() {
Mockito.doNothing()
.when(localInstance)
.makeHelloWorldEntryInTable();
localInstance.printHelloWorld();
}
Case_3: if you have private method, then make it default package level and test it. Thus improves the code coverage.
