* https://github.com/FanJups[Fanon Jupkwo (FanJups)] added a new display name generator extending `org.junit.jupiter.api.DisplayNameGenerator.Standard` to support CamelCase, underscores, and numbers: https://junit-pioneer.org/docs/replace-camelcase-and-underscore-and-number/[ReplaceCamelCaseAndUnderscoreAndNumber] (#793 / #819)

- title: "DisplayName generator to replace CamelCase, underscore and numbers"

url: /docs/replace-camelcase-and-underscore-and-number/

The aim is to simplify unit test display names for method names combining CamelCase, underscore and numbers.

Instead of using the method annotation `org.junit.jupiter.api.DisplayName`, we can just use the class annotation `org.junit.jupiter.api.DisplayNameGeneration` and only use the method annotation if needed.

Applying `@DisplayNameGeneration(ReplaceCamelCaseAndUnderscoreAndNumber.class)` to the test class will provide human-readable descriptions for test methods not annotated with `@DisplayName`.

* Each uppercase letter is turned into its lowercase value prepended by a space.

* Each underscore is turned into a space. Words bounded by underscores or just starting with underscore are not transformed. Usually, these words represent classes or variables.

* Each number is prepended by a space.

== `@DisplayNameGeneration(ReplaceCamelCaseAndUnderscoreAndNumber.class)`

Usage Example:

[source,java,indent=0]

=== Method 1

Generated display name: `Should return error when maxResults is negative`

[source,java,indent=0]

=== Method 2

Generated display name: `Should create limit with range (String)`

[source,java,indent=0]

=== Method 3

Generated display name: `Should return 5 errors (int)`

[source,java,indent=0]

=== Method 4

Generated display name: `Should return 5 errors`

[source,java,indent=0]

=== Method 5

Generated display name: `Should return 23 errors`

[source,java,indent=0]

=== Method 6

Generated display name: `Should return the value of maxResults`

[source,java,indent=0]

=== Method 7

Generated display name: `Should return the number of errors as numberOfErrors inferior or equal to 5 (String)`

[source,java,indent=0]

=== Method 8

Generated display name: `Should return the number of errors as numberOfErrors inferior or equal to 15`

[source,java,indent=0]

=== Method 9

Generated display name: `@DisplayName prevails`

[source,java,indent=0]

package org.junitpioneer.jupiter.displaynamegenerator;

import org.junit.jupiter.api.DisplayName;

import org.junit.jupiter.api.DisplayNameGeneration;

import org.junit.jupiter.api.Test;

import org.junit.jupiter.params.ParameterizedTest;

import org.junit.jupiter.params.provider.ValueSource;

public class ReplaceCamelCaseAndUnderscoreAndNumberDemo {

// tag::class_using_replace_camel_case_and_underscore_and_number_generator[]

@DisplayNameGeneration(ReplaceCamelCaseAndUnderscoreAndNumber.class)

class ReplaceCamelCaseAndUnderscoreAndNumberStyleTest {

// tag::shouldReturnErrorWhen_maxResults_IsNegative[]

@Test

void shouldReturnErrorWhen_maxResults_IsNegative() {

}

// end::shouldReturnErrorWhen_maxResults_IsNegative[]

// tag::shouldCreateLimitWithRange[]

@ParameterizedTest

@ValueSource(strings = { "", " " })

void shouldCreateLimitWithRange(String input) {

}

// end::shouldCreateLimitWithRange[]

// tag::shouldReturn5Errors[]

@ParameterizedTest

@ValueSource(ints = { 5, 23 })

void shouldReturn5Errors(int input) {

}

// end::shouldReturn5Errors[]

// tag::shouldReturn5errors_no_params[]

@Test

void shouldReturn5errors() {

}

// end::shouldReturn5errors_no_params[]

// tag::shouldReturn23Errors[]

@Test

void shouldReturn23Errors() {

}

// end::shouldReturn23Errors[]

// tag::shouldReturnTheValueOf_maxResults[]

@Test

void shouldReturnTheValueOf_maxResults() {

}

// end::shouldReturnTheValueOf_maxResults[]

// tag::shouldReturnTheNumberOfErrorsAs_numberOfErrors_InferiorOrEqualTo5[]

@ParameterizedTest

@ValueSource(strings = { "", " " })

void shouldReturnTheNumberOfErrorsAs_numberOfErrors_InferiorOrEqualTo5(String input) {

}

// end::shouldReturnTheNumberOfErrorsAs_numberOfErrors_InferiorOrEqualTo5[]

// tag::shouldReturnTheNumberOfErrorsAs_numberOfErrors_InferiorOrEqualTo15[]

@Test

void shouldReturnTheNumberOfErrorsAs_numberOfErrors_InferiorOrEqualTo15() {

}

// end::shouldReturnTheNumberOfErrorsAs_numberOfErrors_InferiorOrEqualTo15[]

// tag::testDisplayNamePrevails[]

@DisplayName("@DisplayName prevails")

@Test

void testDisplayNamePrevails() {

}

// end::testDisplayNamePrevails[]

}

// end::class_using_replace_camel_case_and_underscore_and_number_generator[]

}

package org.junitpioneer.jupiter.displaynamegenerator;

exports org.junitpioneer.jupiter.displaynamegenerator;

opens org.junitpioneer.jupiter.displaynamegenerator to org.junit.platform.commons;

package org.junitpioneer.jupiter.displaynamegenerator;

import java.lang.reflect.Method;

import java.util.ArrayList;

import java.util.List;

import org.junit.jupiter.api.DisplayNameGenerator;

public class ReplaceCamelCaseAndUnderscoreAndNumber extends DisplayNameGenerator.Standard {

public static final DisplayNameGenerator INSTANCE = new ReplaceCamelCaseAndUnderscoreAndNumber();

private ReplaceCamelCaseAndUnderscoreAndNumber() {

}

@Override

public String generateDisplayNameForMethod(Class<?> testClass, Method testMethod) {

if (hasParameters(testMethod)) {

return replaceCamelCaseAndUnderscoreAndNumber(testMethod.getName()) + " "

+ DisplayNameGenerator.parameterTypesAsString(testMethod);

}

return replaceCamelCaseAndUnderscoreAndNumber(testMethod.getName());

}

private String replaceCamelCaseAndUnderscoreAndNumber(String input) {

// Remove leading underscore(s)

var sanitized = input.replaceAll("^_+(.*)$", "$1");

List<String> list = new ArrayList<>();

String[] split = sanitized.split("_");

for (int i = 0; i < split.length; i++) {

if (i % 2 == 1) {

// If parity is odd, we are between two underscores, no formatting necessary

list.add(split[i]);

} else {

list.add(formatCamelCase(split[i]));

}

}

// Some cases can lead to double spaces - i.e.: underscore (closing) followed by capital letter

var joined = String.join(" ", list).replaceAll("\\s{2}", " ");

// Capitalize the first letter

return joined.substring(0, 1).toUpperCase() + joined.substring(1);

}

private String formatCamelCase(String in) {

return in.replaceAll("(\\d+)", " $1").replaceAll("([A-Z]+)", " $1").toLowerCase();

}

private boolean hasParameters(Method method) {

return method.getParameterCount() > 0;

}

}

package org.junitpioneer.jupiter.displaynamegenerator;

exports org.junitpioneer.jupiter.displaynamegenerator;

opens org.junitpioneer.jupiter.displaynamegenerator to org.junit.platform.commons;