diff --git a/tests/phpunit/tests/l10n/getLocale.php b/tests/phpunit/tests/l10n/getLocale.php
new file mode 100644
index 0000000000..4c4fe8bb02
--- /dev/null
+++ b/tests/phpunit/tests/l10n/getLocale.php
@@ -0,0 +1,95 @@
+<?php
+
+/**
+ * @group l10n
+ * @group i18n
+ */
+class Tests_L10n_GetLocale extends WP_UnitTestCase {
+	public function test_should_respect_locale_global() {
+		global $locale;
+		$old_locale = $locale;
+
+		$locale = 'foo';
+
+		$found = get_locale();
+		$locale = $old_locale;
+
+		$this->assertSame( 'foo', $found );
+	}
+
+	public function test_local_option_should_take_precedence_on_multisite() {
+		global $locale;
+		$old_locale = $locale;
+		$locale = null;
+
+		if ( ! is_multisite() ) {
+			$this->markTestSkipped( __METHOD__ . ' requires Multisite' );
+		}
+
+		update_option( 'WPLANG', 'en_GB' );
+		update_site_option( 'WPLANG', 'es_ES' );
+
+		$found = get_locale();
+		$locale = $old_locale;
+
+		$this->assertSame( 'en_GB', $found );
+	}
+
+	public function test_network_option_should_be_fallback_on_multisite() {
+		global $locale;
+		$old_locale = $locale;
+		$locale = null;
+
+		if ( ! is_multisite() ) {
+			$this->markTestSkipped( __METHOD__ . ' requires Multisite' );
+		}
+
+		update_site_option( 'WPLANG', 'es_ES' );
+
+		$found = get_locale();
+		$locale = $old_locale;
+
+		$this->assertSame( 'es_ES', $found );
+	}
+
+	public function test_option_should_be_respected_on_nonmultisite() {
+		global $locale;
+		$old_locale = $locale;
+		$locale = null;
+
+		if ( is_multisite() ) {
+			$this->markTestSkipped( __METHOD__ . ' does not apply to Multisite' );
+		}
+
+		update_option( 'WPLANG', 'es_ES' );
+
+		$found = get_locale();
+		$locale = $old_locale;
+
+		$this->assertSame( 'es_ES', $found );
+
+	}
+
+	public function test_should_fall_back_on_en_US() {
+		global $locale;
+		$old_locale = $locale;
+		$locale = null;
+
+		$found = get_locale();
+		$locale = $old_locale;
+
+		$this->assertSame( 'en_US', $found );
+	}
+
+	public function test_should_respect_get_locale_filter() {
+		add_filter( 'locale', array( $this, 'filter_get_locale' ) );
+		$found = get_locale();
+		remove_filter( 'locale', array( $this, 'filter_get_locale' ) );
+
+		$this->assertSame( 'foo', $found );
+	}
+
+	public function filter_get_locale() {
+		return 'foo';
+	}
+}