PHPUnit assertStringEqualsFile() Function

The assertStringEqualsFile() function is a builtin function in PHPUnit and is used to assert whether the actual string content obtained is equaled to the expected file or not. This assertion will return true in the case if the expected file content is the same as the actual string content else returns false. In case of true the asserted test case got passed else test case got failed.

Syntax:

assertStringEqualsFile(string $expectedFile, 
string $actualString[, string $message = ''])

Parameters: This function accepts three parameters as mentioned above and described below:

• $expectedfile: This parameter is of any type which represents the expected file.
• $actualstring: This parameter is of any type which represents the actual string content.
• $message: This parameter takes a string value. When the test case got failed this string message got displayed as an error message.

Below examples illustrate the assertStringEqualsFile() function in PHPUnit:

Example 1:

PHP

<?php
use PHPUnit\Framework\TestCase;

class GeeksPhpunitTestCase extends TestCase
{
    public function testNegativeTestcaseForassertStringEqualsFile()
    {
        $expectedfile = "/home/lovely/Documents/php/abc";
        $actualstring = "File has geeksforgeeks";

        // Assert function to test whether
        // expected file content is equal to
        // actual string content or not
        $this->assertStringEqualsFile(
            $expectedfile,
            $actualstring,
            "actual string content is equals to
             expected file content or not"
        );
    }
}

?>

Output:

PHPUnit 8.5.8 by Sebastian Bergmann and contributors.

F                                                         1 / 1 (100%)

Time: 89 ms, Memory: 10.00 MB

There was 1 failure:

1) GeeksPhpunitTestCase::testNegativeTestcaseForassertStringEqualsFile
actual string content is not equals to expected file content
Failed asserting that two strings are equal.
--- Expected
+++ Actual
@@ @@
-'File has not geeksforgeeks'
+'File has geeksforgeeks'

/home/lovely/Documents/php/test.php:17

FAILURES!
Tests: 1, Assertions: 2, Failures: 1.

Example 2:

PHP

<?php
use PHPUnit\Framework\TestCase;

class GeeksPhpunitTestCase extends TestCase
{
    public function testPositiveTestcaseForassertStringEqualsFile()
    {
        $expectedfile = "/home/lovely/Documents/php/abc";
        $actualstring = "File has geeksforgeeks";

        // Assert function to test whether
        // expected file content is equal
        // to actual string content or not
        $this->assertStringEqualsFile(
            $expectedfile,
            $actualstring,
            "actual string content is equals
             to expected file content or not"
        );
    }
}

?>

Output:

PHPUnit 8.5.8 by Sebastian Bergmann and contributors.

.                                                  1 / 1 (100%)

Time: 87 ms, Memory: 10.00 MB

OK (1 test, 2 assertions)

Reference: https://phpunit.readthedocs.io/en/9.2/assertions.html#assertstringequalsfile