diff --git a/tests/ValueParsers/Normalizers/SentenceCapitalizer.php b/tests/ValueParsers/Normalizers/SentenceCapitalizer.php
new file mode 100644
index 0000000..14af4e3
--- /dev/null
+++ b/tests/ValueParsers/Normalizers/SentenceCapitalizer.php
@@ -0,0 +1,54 @@
+<?php
+
+namespace ValueParsers\Normalizers\Test;
+
+use DataValues\StringValue;
+use PHPUnit_Framework_TestCase;
+use ValueParsers\Normalizers\TrimmingStringNormalizer;
+
+/**
+ * @covers \ValueParsers\Normalizers\TrimmingStringNormalizer
+ *
+ * @group ValueParsers
+ * @group DataValueExtensions
+ *
+ * @license GPL-2.0-or-later
+ * @author Thiemo Kreuz
+ */
+class TrimmingStringNormalizerTest extends PHPUnit_Framework_TestCase {
+
+	/**
+	 * @dataProvider stringProvider
+	 */
+	public function testNormalize( $value, $expected ) {
+		$normalizer = new TrimmingStringNormalizer();
+		$this->assertSame( $expected, $normalizer->normalize( $value ) );
+	}
+
+	public function stringProvider() {
+		return [
+			'Removed underscore' => [ 'example_', 'Example' ],
+			'lowercase' => [ 'examPle', 'Example' ],
+		];
+	}
+
+	/**
+	 * @dataProvider invalidValueProvider
+	 */
+	public function testNormalizeException( $value ) {
+		$normalizer = new TrimmingStringNormalizer();
+		$this->setExpectedException( 'InvalidArgumentException' );
+		$normalizer->normalize( $value );
+	}
+
+	public function invalidValueProvider() {
+		return [
+			[ null ],
+			[ true ],
+			[ 1 ],
+			[ new StringValue( '' ) ],
+		];
+	}
+
+}
+