Writing Custom Annotations

Need for creating custom annotations #

We can create custom annotations and use them using TestNG configurations methods to make annotations more customizable per your needs.

Example of custom annotation #

As a demonstration, we will create a single @DataProvider method that reads from different files with a file to read given in a test method.

An annotation that is applicable to methods that pass on the file path to read data from:

@Retention(java.lang.annotation.RetentionPolicy.RUNTIME)
@Target(java.lang.annotation.ElementType.METHOD)
public @interface DataProviderFile {

	String file() default "";
}

DataProviderFactory class containing the @DataProvider methods:

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;

public class DataProviderFactory {

	@DataProvider(name = "data")
	public static Iterator<Object[]> getData(Method method) throws IOException {
		DataProviderFile file = method.getAnnotation(DataProviderFile.class);
		if (file != null) {
			List<Object[]> list = new ArrayList<>();
			for (String line : Files.readAllLines(Paths.get(file.file()))) {
				list.add(new Object[] { line });
			}
			return list.iterator();
		}
		return Collections.emptyIterator();
	}
}

In the above code snippet, we are getting the file path that is passed to the @DataProvider method using @DataProviderFile annotation and transforming the lines in the file to Object[] and returning as Iterator<Object[]> as expected from @DataProvider method.

Test Class passing different files to read from:

public class DataProviderExample {

	@DataProviderFile(file = "sampleA.txt")
	@Test(dataProvider = "data", dataProviderClass = DataProviderFactory.class)
	public void testA(String line) {
		assertNotNull(line);
	}

	@DataProviderFile(file = "sampleB.txt")
	@Test(dataProvider = "data", dataProviderClass = DataProviderFactory.class)
	public void testB(String line) {
		assertNotNull(line);
	}

}

In the above test class, both the test methods are using the same @DataProvider method but reading from different files that are passed using @DataProviderFile. Thus, we are reusing the same @DataProvider method instead of writing two different ones.

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That is it for the details of the TestNG framework. You now know how the different functionalities provide support for effective testing of a UI. There is a quiz in the next lesson for you to solve.