`@CsvSource` drops backslash character from input

[xazap]

I am seeing issues with backslash characters getting dropped while processing input from @CsvSource annotated tests. I observed that its occurrence depends on the test case that preceded it as is shown in the reproduction steps. I have considered it might be related to having single quote characters in the input so I deliberately set quoteCharacter='x' in the @CsvSource annotation.

Steps to reproduce

This test passes as expected:

@ParameterizedTest(name = "[{index}] {arguments}")
@CsvSource(useHeadersInDisplayName = true, delimiterString = "||", quoteCharacter = 'x', textBlock = """
	INPUT		|| EXPECTED LENGTH
	\\M\\\\o\\\'	|| 7
	\\M\\q\\\'	|| 6
""")
void test1(String input, int expectedLength) {
	Assertions.assertTrue(input.length() == expectedLength);
}

If I swap the input lines, the test unexpectedly fails because the String "\\M\\\\o\\\'" is missing a backslash character before 'o' resulting in a length of 6 and thus failing the test:

@ParameterizedTest(name = "[{index}] {arguments}")
@CsvSource(useHeadersInDisplayName = true, delimiterString = "||", quoteCharacter = 'x', textBlock = """
	INPUT		|| EXPECTED LENGTH
	\\M\\q\\\'	|| 6
	\\M\\\\o\\\'	|| 7
""")
void test2(String input, int expectedLength) {
	Assertions.assertTrue(input.length() == expectedLength);
}

To further show that a backlash character gets eaten, I added an extra '\\' character to the input. The test now passes, but note that the String "\\M\\\\\\o\\\'" should have a length of 8, not 7!

@ParameterizedTest(name = "[{index}] {arguments}")
@CsvSource(useHeadersInDisplayName = true, delimiterString = "||", quoteCharacter = 'x', textBlock = """
	INPUT		|| EXPECTED LENGTH
	\\M\\q\\\'	|| 6
	\\M\\\\\\o\\\'	|| 7
""")
void test3(String input, int expectedLength) {
	Assertions.assertTrue(input.length() == expectedLength);
}

Context

• Jupiter version: 5.11.0-M1 (also tried: 5.10.2, same results)
• Plaform version: 1.11.0-M1 (also tried: 1.10.2, same results)
• Java 17
• Build Tool/IDE: Maven 3.9.4 / Eclipse 2024.3

[Marc Philipp]

I've tried reproducing the issue with this test class:

package com.example.project;

import org.junit.jupiter.params.ParameterizedTest;
import org.junit.jupiter.params.provider.CsvSource;

import static org.junit.jupiter.api.Assertions.assertEquals;

public class ParamEscapingTests {

    @ParameterizedTest(name = "[{index}] {arguments}")
    @CsvSource(useHeadersInDisplayName = true, delimiterString = "||", quoteCharacter = 'x', textBlock = """
        INPUT		    || EXPECTED LENGTH
        \\M\\\\o\\\'	|| 7
        \\M\\q\\\'	    || 6
    """)
    void test1(String input, int expectedLength) {
        assertEquals(expectedLength, input.length());
    }

    @ParameterizedTest(name = "[{index}] {arguments}")
    @CsvSource(useHeadersInDisplayName = true, delimiterString = "||", quoteCharacter = 'x', textBlock = """
        INPUT		    || EXPECTED LENGTH
        \\M\\q\\\'	    || 6
        \\M\\\\o\\\'	|| 7
    """)
    void test2(String input, int expectedLength) {
        assertEquals(expectedLength, input.length());
    }

    @ParameterizedTest(name = "[{index}] {arguments}")
    @CsvSource(useHeadersInDisplayName = true, delimiterString = "||", quoteCharacter = 'x', textBlock = """
        INPUT		    || EXPECTED LENGTH
        \\M\\q\\\'	    || 6
        \\M\\\\\\o\\\'	|| 7
    """)
    void test3(String input, int expectedLength) {
        assertEquals(expectedLength, input.length());
    }
}

However, for me all tests but the last pass as expected. I have tried with Maven and Gradle on Java 17.0.10. Not sure if Eclipse plays a part here. Are you using the Eclipse compiler or Maven? One thing IntelliJ flagged was the unnecessary escaping of ', meaning \\M\\\\o\\\' should be the same as \\M\\\\o\\'.

[Marc Philipp]

One thing IntelliJ flagged was the unnecessary escaping of ', meaning \\M\\\\o\\\' should be the same as \\M\\\\o\\'.

Ok, I tried in Eclipse now. The "unnecessary escaping" seems to be causing the issue when running from Eclipse. It works as expected after removing it.

[xazap]

I can confirm the tests pass except the last one when running a Maven build that is using the Oracle compiler. So it seems there is difference in behavior between Eclipse and Oracle compiler.

I can also conform that removing the "unnecessary escaping" fixes the problem when running in Eclipse. Still, the behaviour in Eclipse is weird. As far as I know escaping a quote is legal in a String. I might take this up with the ECJ project to see whether Eclipse compiler is actually parsing correctly. It does not seem like an issue with @CvsSource. Thanks for looking into this!