diff --git a/app/src/test/java/com/d4rk/androidtutorials/java/utils/CodeHighlighterTest.java b/app/src/test/java/com/d4rk/androidtutorials/java/utils/CodeHighlighterTest.java
new file mode 100644
index 00000000..45ee4c70
--- /dev/null
+++ b/app/src/test/java/com/d4rk/androidtutorials/java/utils/CodeHighlighterTest.java
@@ -0,0 +1,46 @@
+package com.d4rk.androidtutorials.java.utils;
+
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.anyInt;
+import static org.mockito.Mockito.inOrder;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.times;
+
+import com.amrdeveloper.codeview.CodeView;
+
+import org.junit.Test;
+import org.mockito.InOrder;
+
+import java.util.regex.Pattern;
+
+/**
+ * Tests for {@link CodeHighlighter}.
+ */
+public class CodeHighlighterTest {
+
+    @Test
+    public void applyJavaTheme_resetsPatternsAndReHighlights() {
+        CodeView codeView = mock(CodeView.class);
+
+        CodeHighlighter.applyJavaTheme(codeView);
+
+        InOrder order = inOrder(codeView);
+        order.verify(codeView).resetSyntaxPatternList();
+        order.verify(codeView).resetHighlighter();
+        order.verify(codeView, times(5)).addSyntaxPattern(any(Pattern.class), anyInt());
+        order.verify(codeView).reHighlightSyntax();
+    }
+
+    @Test
+    public void applyXmlTheme_resetsPatternsAndReHighlights() {
+        CodeView codeView = mock(CodeView.class);
+
+        CodeHighlighter.applyXmlTheme(codeView);
+
+        InOrder order = inOrder(codeView);
+        order.verify(codeView).resetSyntaxPatternList();
+        order.verify(codeView).resetHighlighter();
+        order.verify(codeView, times(4)).addSyntaxPattern(any(Pattern.class), anyInt());
+        order.verify(codeView).reHighlightSyntax();
+    }
+}
diff --git a/app/src/test/java/com/d4rk/androidtutorials/java/utils/CodeViewUtilsTest.java b/app/src/test/java/com/d4rk/androidtutorials/java/utils/CodeViewUtilsTest.java
index 7c630d5f..6bb2dbdd 100644
--- a/app/src/test/java/com/d4rk/androidtutorials/java/utils/CodeViewUtilsTest.java
+++ b/app/src/test/java/com/d4rk/androidtutorials/java/utils/CodeViewUtilsTest.java
@@ -26,12 +26,24 @@ private void verifyDefaults(CodeView view, Typeface typeface) {
     }
 
     @Test
-    public void applyDefaults_configuresAllViews() {
+    public void applyDefaults_configuresNonNullViews() {
         Typeface typeface = mock(Typeface.class);
         CodeView first = mock(CodeView.class);
         CodeView second = mock(CodeView.class);
 
-        CodeViewUtils.applyDefaults(typeface, first, second, null);
+        CodeViewUtils.applyDefaults(typeface, first, second);
+
+        verifyDefaults(first, typeface);
+        verifyDefaults(second, typeface);
+    }
+
+    @Test
+    public void applyDefaults_ignoresNullViews() {
+        Typeface typeface = mock(Typeface.class);
+        CodeView first = mock(CodeView.class);
+        CodeView second = mock(CodeView.class);
+
+        CodeViewUtils.applyDefaults(typeface, null, first, null, second, null);
 
         verifyDefaults(first, typeface);
         verifyDefaults(second, typeface);