diff --git a/tests/phpunit/tests/functions/WpValidateBoolean.php b/tests/phpunit/tests/functions/WpValidateBoolean.php
new file mode 100644
index 0000000000..812563757e
--- /dev/null
+++ b/tests/phpunit/tests/functions/WpValidateBoolean.php
@@ -0,0 +1,59 @@
+<?php
+
+/**
+ * @group functions.php
+ */
+class Tests_Functions_WpValidateBoolean extends WP_UnitTestCase {
+	public function test_bool_true() {
+		$this->assertTrue( wp_validate_boolean( true ) );
+	}
+
+	public function test_int_1() {
+		$this->assertTrue( wp_validate_boolean( 1 ) );
+	}
+
+	public function test_string_true_lowercase() {
+		$this->assertTrue( wp_validate_boolean( 'true' ) );
+	}
+
+	public function test_string_true_uppercase() {
+		$this->assertTrue( wp_validate_boolean( 'TRUE' ) );
+	}
+
+	public function test_arbitrary_string_should_return_true() {
+		$this->assertTrue( wp_validate_boolean( 'foobar' ) );
+	}
+
+	public function test_bool_false() {
+		$this->assertFalse( wp_validate_boolean( false ) );
+	}
+
+	public function test_int_0() {
+		$this->assertFalse( wp_validate_boolean( 0 ) );
+	}
+
+	public function test_float_0() {
+		$this->assertFalse( wp_validate_boolean( 0.0 ) );
+	}
+
+	public function test_empty_string() {
+		$this->assertFalse( wp_validate_boolean( '' ) );
+	}
+
+	public function test_string_0() {
+		$this->assertFalse( wp_validate_boolean( '0' ) );
+	}
+
+	public function test_empty_array() {
+		$this->assertFalse( wp_validate_boolean( array() ) );
+	}
+
+	public function test_null() {
+		$this->assertFalse( wp_validate_boolean( null ) );
+	}
+
+	public function test_string_false_lowercase() {
+		// Differs from (bool) conversion.
+		$this->assertFalse( wp_validate_boolean( 'false' ) );
+	}
+}