Cucumber DataTable

How to use Cucumber DataTable to create mock tests.

Previously I wrote about setting up Cucumber in IntelliJ.

In a feature file you can create a mock test for an input and assert an output.

For example, an application that reads lines from a text, and extracts specific content, for instance, extract all the numbers from the text.

The .feature file could be the following:

Feature: Extract Digits From File
	Scenario: Extract digits from a text file
		Given I have a text file
			| Mash at 152F for 60 mins |
			| Using Pilsner malt at 82% and 7% Vienna malt. |
			| With an ABV of 7% |
		When I extract the digits from the file
		Then A list of digits is extracted
			| 152 | 60 | 82 | 7 | 7 |

In the steps class file, Given has:

List<List<String>> textFileData;

@Given("I have a text file")
public void i_have_a_text_file(DataTable dataTable) {
	textFileData = new ArrayList<>(dataTable.asLists());
}

If you look at the source code for DataTable, it creates an object of type List<List<String>>. You can convert this object into an ArrayList. If you print textFileData in the above example, it will print:

[ [Mash at 152F for 60 mins], [Using Pilsner malt at 82% and 7% Vienna malt.], [With an ABV of 7%] ]

In the steps class file. Then has:

@Then("A list of digits is extracted")
public void a_list_of_digits_is_extracted(DataTable dataTable) {
	List<Integer> expectedDigits = dataTable.asLists()
		.get(0)
		.stream()
		.map(Integer::parseInt)
		.toList();

The method asLists() converts dataTable to an object of type List<List<String>>. You can do the comparison of objects by printing this:

System.out.println(dataTable.getClass());
System.out.println(dataTable.asLists().getClass());

If you print dataTable.asLists() in the example above, you will get a list of lists with one element:

[ [152, 60 , 82 , 7 , 7 ] ]

These aren’t of type int or Integer though. You can extract the first element in this array with .get(0), convert it to a stream .stream(), map each string number to an Integer .map(Integer::parseInt), and convert it back to a list .toList().

Printing expectedDigits will result in a List<Integer>:

[152, 60 , 82 , 7 , 7 ]

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