Set system property in jmockit unit test

Question

Using a combination of testng and jmockit to do some unit testing. In a method I am testing, it tries to access a system property that I set using a JBoss deploy script, therefore my unit test doesn't have access to the entire JBoss environment to access the properties, so it returns null when testing that method. Tried mocking and setting the system variable directly in my test, but the system property is still returning null in the class that I am testing.

The class being tested:

//returns the correct value in the application but returns null for the test
public static final String webdavrootDir = System.getProperty("property.name");

public String getFileUrl(){
       StringBuilder sb = new StringBuilder();
       return sb.append(webdavrootDir)
               .append(intervalDir)
               .append(fileName)
               .toString();
}

The test:

@Test
    public void getUrl(@Mocked System system){
        system.setProperty("property.name", "https://justatest.com/dav/bulk");
        String fileUrl = csvConfig.getFileUrl();

        assertEquals(fileUrl, "https://justatest.com/dav/bulk/otherstuff");
}

The test finds the value null/otherstuff but expects https://justatest.com/dav/bulk/otherstuff

I have also tried setting the system property in a testng @BeforeMethod method without any success.

score 4 · Accepted Answer · edited Oct 06 '21 at 17:58

Make sure you call System.setProperty("property.name", "https://justatest.com/dav/bulk"); before the class being tested is instantiated, otherwise the static field will always be null.

Consider using a @BeforeClass setup method for this:

@BeforeClass
public static void setup() {
    System.setProperty("property.name", "https://justatest.com/dav/bulk");
    // Instantiate your CsvConfig instance here if applicable.
}

and then

@Test
public void getUrl(){
    System.setProperty("property.name", "https://justatest.com/dav/bulk");
    String fileUrl = csvConfig.getFileUrl();
    assertEquals(fileUrl, "https://justatest.com/dav/bulk/otherstuff");
}

Andy · Answer 2 · 2017-05-31T13:06:34.763

If you want to use jMocki, but you have to make sure it is done, before your class-under-test is beeing loaded (because of the static field).

@BeforeClass
public static void fakeSystemProperty() {
    new MockUp<System>() {

        @Mock
        public String getProperty(String key) {
            return "https://justatest.com/dav/bulk";
        }
    };
}

Another way would be to modify the class-under-test and partially mock this one, e.g.:

public class CsvConfig {
    private static final String webdavrootDir = System.getProperty("property.name");

    public static String getProperty() {
        return webdavrootDir;
    }
}

The test:

@BeforeClass
public static void fakeSystemProperty() {
    new MockUp<CsvConfig>() {

        @Mock
        public String getProperty() {
            return "https://justatest.com/dav/bulk";
        }
    };
}

Set system property in jmockit unit test

2 Answers2