[JAVA] Supports multiple test cases with one method with @ParameterizedTest!

Overview

--When writing a test in Junit, the result or test content may not change, only the input is different. ――At that time, I found it troublesome to create one test method for one test. --I tried using @ParameterizedTest because it can be handled.

What you can do with @ParameterizedTest

--When not in use

    @Test
    public void sample1() {
        assertThat("a".length()).isEqualTo(1);
    }

    @Test
    public void sample2() {
        assertThat("b".length()).isEqualTo(1);
    }

(I won't write such a test, but as a sample ...)

--When using

    @ParameterizedTest
    @ValueSource(strings = {"a", "b"})
    public void sample(String string) {
        assertThat(string.length()).isEqualTo(1);
    }

Like this, you can combine multiple tests just by adding a parameter to the argument of @ ValueSource.

There are several ways to specify the parameters, so I will introduce them below.

• Will be added at any time.

@ValueSource --Used when "one parameter" and "type is basic type" --How to specify arguments changes depending on the parameter type -The value specified by the argument of @ValueSource is received by the argument of the method. ――It seems that you can handle all the basic types, but here I will focus on the ones that I often use.

String --Can handle empty and whitespace characters, but not null --If you want to handle null, use @MethodSource described later.

    @ParameterizedTest
    @ValueSource(strings = {"a", "b", "c"})
    public void string(String value) {
        System.out.println("string: " + value);
    }

Execution result

string: 'a'
string: 'b'
string: 'c'
string: ''
string: '   '

int

    @ParameterizedTest
    @ValueSource(ints = {1, 2 ,3})
    public void ints(int value) {
        System.out.println("ints: " + value);
    }

Execution result

ints: 1
ints: 2
ints: 3

@CsvSource --Use when you want to pass multiple parameters to a method --Parameters are described as strings, and as the name of Csv suggests, multiple parameters are combined separated by commas. --If you specify a number, you can receive either String or ʻint`.

    @ParameterizedTest
    @CsvSource({"1, val1", "2, val2", "3, val3"})
    public void csv(int num, String value) {  //Receive a number as an int
        System.out.println("num: '" + num + "', value: '" + value + "'");
    }

    @ParameterizedTest
    @CsvSource({"1, val1", "2, val2", "3, val3"})
    public void csv(String num, String value) {  //Receive a number as a String
        System.out.println("num: '" + num + "', value: '" + value + "'");
    }

Execution result

num: '1', value: 'val1'
num: '2', value: 'val2'
num: '3', value: 'val3'

--Can handle nulls and empty strings --By default, the leading and trailing whitespace characters are trimmed, but you can leave the leading and trailing whitespace characters by enclosing them in''.

    @ParameterizedTest
    @CsvSource({"Empty string, ''", "Whitespace character, '   '", "null, "})
    public void csv(String type, String value) {
        System.out.println(type + ": '" + value + "'");
    }

Execution result

Empty string: ''
Whitespace character: '   '
null: 'null'

@EnumSource --Can be used when you want to test based on the definition of enum class --If you specify names or mode, you can do include, exclude, etc. --mode defaults to ʻINCLUDE`

Enum class to use

    enum SampleEnum {
        ENUM1,
        ENUM2,
        ENUM3
    }

All cases

    @ParameterizedTest
    @EnumSource(SampleEnum.class)
    public void enumSource(SampleEnum value) {
        System.out.println("enum: " + value);
    }

Execution result

enum: ENUM1
enum: ENUM2
enum: ENUM3

include

    @ParameterizedTest
    @EnumSource(value = SampleEnum.class, names = {"ENUM1", "ENUM2"})
    public void enumInclude(SampleEnum value) {
        System.out.println("enum: " + value);
    }

Execution result

enum: ENUM1
enum: ENUM2

exclude

    @ParameterizedTest
    @EnumSource(value = SampleEnum.class, names = {"ENUM1", "ENUM2"}, mode = EnumSource.Mode.EXCLUDE)
    public void enumExclude(SampleEnum value) {
        System.out.println("enum: " + value);
    }

Execution result

enum: ENUM3

@MethodSource --You can pass any class as an argument by using @MethodSource --Define a static method that returns one of Stream, Iterable, Iterator to pass as an argument --As mentioned above, it can handle null

    @ParameterizedTest
    @MethodSource("source")
    public void methodSource(String value) {
        System.out.println("value: " + value);
    }

    public static Stream<String> source() {
        return Stream.of("string1", "string2", null);
    }

Execution result

value: string1
value: string2
value: null