JUnit's @CsvSource.quoteCharacter

@CsvSource used with text blocks is really awesome! Similarly to validation files, it can be used to create easily readable tests with readily visible inputs and outputs placed side by side.

For example:

    @ParameterizedTest
    @CsvSource(delimiterString = "->", textBlock = """
        ABC -> abc
        Abc -> abc
        """)
    void toLowercase(String input, String expected) {
        assertThat(input.toLowerCase())
            .isEqualTo(expected);
    }

What recently confused me was the following error:

org.junit.jupiter.api.extension.ParameterResolutionException:
No ParameterResolver registered for parameter [java.lang.String arg1] in method [void MyTest.test(java.lang.String,java.lang.String)].

It came out that it was caused by a parameter value starting with a single quote ', that wasn't closed by another ' at the end of value. In my case the culprit was 'S-GRAVENHAGE, which is Belgian street name.

The solution is to set parameter quoteCharacter to double quote ", provided we are using text block. This way we can test empty string with "".

Example:

    @ParameterizedTest
    @CsvSource(quoteCharacter = '\"', delimiterString = "->", textBlock = """
        'S-GRAVENHAGE -> 's-gravenhage
        "" -> ""
        """)
    void toLowercase(String input, String expected) {
        assertThat(input.toLowerCase())
            .isEqualTo(expected);
    }

I hope it was helpful, cheers!