Introduction

In this post, we will cover how to use CSV string or file as a source of parameters for unit tests. Junit has some handy annotations that help you with reading a CSV source and using its contents as parameters for a unit test.

To use these annotations, you need the following dependencies. The first one is for Junit itself and the second one is for the JUnit parameterized tests. This last dependency includes the annotations we need.

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<dependency>
    <groupId>org.junit.jupiter</groupId>
    <artifactId>junit-jupiter-engine</artifactId>
    <version>5.9.2</version>
    <scope>test</scope>
</dependency>

<dependency>
    <groupId>org.junit.jupiter</groupId>
    <artifactId>junit-jupiter-params</artifactId>
    <version>5.9.2</version>
    <scope>test</scope>
</dependency>

CSV source inside an annotation

If you don't have a lot of values you need to test you can put them inside the annotation like is done in the following example. You need to place the two annotations on your test to make it work. @ParameterizedTest tells JUnit that your tests need parameters to run. The @CsvSource lets you define what the parameters should be in CSV format.

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@ParameterizedTest
@CsvSource({
        "Noah,   20",
        "James,  22",
        "Evelyn, 35",
        "Harper, 58"
})
void testWithCsvSource(String name, int age) {
    assertTrue(name.length() > 2);
    assertTrue(age >= 20);
}

CSV files as source

When you need a lot of values, and it gets too big or messy to define them inside the test class, you can also place them inside a file. To do this you would need the @ParameterizedTest to tell Junit that your tests need parameters. The @CsvFileSource lets you define which file you want to read the values from. In the following example the values from /values.csv are used for the test.

The values.csv file is placed inside the test/resource directory.

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@ParameterizedTest
@CsvFileSource(resources = "/values.csv", numLinesToSkip = 1, encoding = "UTF-8" )
void testWithCsvFileResource(String name, int age) {
    assertTrue(name.length() > 2);
    assertTrue(age >= 20);
}

Array of CSV files as source

You can also use multiple CSV files as the source for a unit test. To use multiple CSV files you need to define them in an array like this: resources = {"/values.csv", "/more-values.csv"}. The following example reads the values from the following files: values.csv and more-values.csv.

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@ParameterizedTest
@CsvFileSource(resources = {"/values.csv", "/more-values.csv"}, numLinesToSkip = 1, encoding = "UTF-8" )
void testWithCsvFileResource(String name, int age) {
    assertTrue(name.length() > 2);
    assertTrue(age >= 20);
}

The values.csv file

This is what the values.csv file from the previous examples looks like:

Name,age
Noah,20
James,22
Evelyn,35
Harper,58

Conclusion

in this post, we took a look at how to read parameters for a unit test from a CSV file. The first example shows how to define and use a CSV array inside the test class. The example shows how to