I have a huge JSON-File which contains testcases. (No I don't wanna show it here because it doesn't matter in this case to know the file) I parse the json file to my junit test - that works fine. But I've got 50 testcases and if I want to show each in Junit like: "test 0 from 50 passed" and have a list like: test 1 passed, test 2 passed, test 3 failed..
I have to put each testcase into a method. How can I dynamically do this? Is this possible in Junit? Because when I'm parsing the json, I don't know how many cases I have.
JUnit has direct support for CSV files, which means you can import and use them easily using @CSVFileSource.
However, since your case does not involve CSV files, I tried to create parametrized tests in JUnit 5 using JSON files.
Our class under test.
public class MathClass {
public static int add(int a, int b) {
return a + b;
}
}
Here's the JSON file I am using.
[
{
"name": "add positive numbers",
"cases": [[1, 1, 2],[2, 2, 4]]
},
{
"name": "add negative numbers",
"cases": [[-1, -1, -2 ], [-10, -10, -20 ]]
}
]
So, in JUnit 5 there is an annotation called @MethodSource which gives you the opportunity to provide arguments to your parametrized test. You only need to provide the method name. Here's my argument provider method.
@SneakyThrows
private static Stream<TestCase> getAddCases() {
final ObjectMapper mapper = new ObjectMapper();
TypeReference<List<Case>> typeRef = new TypeReference<>() {};
final File file = new File("src/test/resources/add-cases.json");
final List<Case> cases = mapper.readValue(file, typeRef);
return cases.stream()
.flatMap(caze -> caze.getCases()
.stream()
.map(el -> new TestCase(caze.getName(), el)));
}
In the code above, the class Case is used to map from the json object to Java Object and since the "cases" field is a multidimensional array, to represent each test case there is a class called TestCase. (Overall, this is not important for you, since you already are able to parse it, but I wanted to put it here anyway).
Finally, the test method itself.
@ParameterizedTest(name = "{index} : {arguments}")
@MethodSource("getAddCases")
void add_test(TestCase testCase) {
final List<Integer> values = testCase.getValues();
int i1 = values.get(0);
int i2 = values.get(1);
int e = values.get(2);
assertEquals(e, MathClass.add(i1, i2));
}
@ParametrizedTest annotation takes a name argument where you can provide a template for the test names. I just played around with the toString method of TestCase class to achieve a better description for each test case.
@Override
public String toString() {
return String.format("%s : (%s, %s) ==> %s", name, values.get(0), values.get(1), values.get(2));
}
And voila!
