Writing Custom Annotations

In this topic, we will see how to create a custom annotation and hookup with TestNG configuration methods.

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.


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.

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