diff --git a/tests/phpunit/tests/compat/arrayIsList.php b/tests/phpunit/tests/compat/arrayIsList.php
new file mode 100644
index 0000000000..90e500103e
--- /dev/null
+++ b/tests/phpunit/tests/compat/arrayIsList.php
@@ -0,0 +1,115 @@
+<?php
+
+/**
+ * @group compat
+ *
+ * @covers ::array_is_list
+ */
+class Tests_Compat_arrayIsList extends WP_UnitTestCase {
+
+	/**
+	 * Test that array_is_list() is always available (either from PHP or WP).
+	 *
+	 * @ticket 55105
+	 */
+	public function test_array_is_list_availability() {
+		$this->assertTrue( function_exists( 'array_is_list' ) );
+	}
+
+	/**
+	 * @dataProvider data_array_is_list
+	 *
+	 * @ticket 55105
+	 *
+	 * @param bool  $expected Whether the array is a list.
+	 * @param array $arr      The array.
+	 */
+	public function test_array_is_list( $expected, $arr ) {
+		$this->assertSame( $expected, array_is_list( $arr ) );
+	}
+
+	/**
+	 * Data provider.
+	 *
+	 * @return array[]
+	 */
+	public function data_array_is_list() {
+		return array(
+			'empty array'                   => array(
+				'expected' => true,
+				'arr'      => array(),
+			),
+			'array(NAN)'                    => array(
+				'expected' => true,
+				'arr'      => array( NAN ),
+			),
+			'array( INF )'                  => array(
+				'expected' => true,
+				'arr'      => array( INF ),
+			),
+			'consecutive int keys from 0'   => array(
+				'expected' => true,
+				'arr'      => array(
+					0 => 'one',
+					1 => 'two',
+				),
+			),
+			'consecutive float keys from 0' => array(
+				'expected' => true,
+				'arr'      => array(
+					0.0 => 'one',
+					1.0 => 'two',
+				),
+			),
+			'consecutive str keys from 0'   => array(
+				'expected' => true,
+				'arr'      => array(
+					'0' => 'one',
+					'1' => 'two',
+				),
+			),
+			'consecutive int keys from 1'   => array(
+				'expected' => false,
+				'arr'      => array(
+					1 => 'one',
+					2 => 'two',
+				),
+			),
+			'consecutive float keys from 1' => array(
+				'expected' => false,
+				'arr'      => array(
+					1.0 => 'one',
+					2.0 => 'two',
+				),
+			),
+			'consecutive str keys from 1'   => array(
+				'expected' => false,
+				'arr'      => array(
+					'1' => 'one',
+					'2' => 'two',
+				),
+			),
+			'non-consecutive int keys'      => array(
+				'expected' => false,
+				'arr'      => array(
+					1 => 'one',
+					0 => 'two',
+				),
+			),
+			'non-consecutive float keys'    => array(
+				'expected' => false,
+				'arr'      => array(
+					1.0 => 'one',
+					0.0 => 'two',
+				),
+			),
+			'non-consecutive string keys'   => array(
+				'expected' => false,
+				'arr'      => array(
+					'1' => 'one',
+					'0' => 'two',
+				),
+			),
+		);
+	}
+}