diff --git a/test/printer-utils-tests.js b/test/printer-utils-tests.js
new file mode 100644
index 0000000..46b9f34
--- /dev/null
+++ b/test/printer-utils-tests.js
@@ -0,0 +1,79 @@
+var assert = require('assert');
+
+var PrinterUtils = require('../src/printer-utils.js').PrinterUtils;
+
+describe('Utils', function() {
+  describe('getHtmlId', function() {
+    it('should generate file unique id', function() {
+      var result = PrinterUtils.getHtmlId({
+        oldName: 'sample.js',
+        newName: 'sample.js'
+      });
+      assert.equal('d2h-960013', result);
+    });
+  });
+
+  describe('getDiffName', function() {
+    it('should generate the file name for a changed file', function() {
+      var result = PrinterUtils.getDiffName({
+        oldName: 'sample.js',
+        newName: 'sample.js'
+      });
+      assert.equal('sample.js', result);
+    });
+    it('should generate the file name for a changed file and renamed', function() {
+      var result = PrinterUtils.getDiffName({
+        oldName: 'sample1.js',
+        newName: 'sample2.js'
+      });
+      assert.equal('sample1.js -> sample2.js', result);
+    });
+    it('should generate the file name for a deleted file', function() {
+      var result = PrinterUtils.getDiffName({
+        oldName: 'src/my/file.js',
+        newName: '/dev/null'
+      });
+      assert.equal('src/my/file.js', result);
+    });
+    it('should generate the file name for a new file', function() {
+      var result = PrinterUtils.getDiffName({
+        oldName: '/dev/null',
+        newName: 'src/my/file.js'
+      });
+      assert.equal('src/my/file.js', result);
+    });
+  });
+
+  describe('diffHighlight', function() {
+    it('should highlight two lines', function() {
+      var result = PrinterUtils.diffHighlight(
+        'var myVar = 2;',
+        'var myVariable = 3;',
+        {matching: 'words'}
+      );
+
+      assert.deepEqual({
+        first: {prefix: 'v', line: 'ar <del>myVar</del> = <del>2</del>;'},
+        second: {
+          prefix: 'v',
+          line: 'ar <ins>myVariable</ins> = <ins>3</ins>;'
+        }
+      }, result);
+    });
+    it('should highlight two lines char by char', function() {
+      var result = PrinterUtils.diffHighlight(
+        'var myVar = 2;',
+        'var myVariable = 3;',
+        {charByChar: true}
+      );
+
+      assert.deepEqual({
+        first: {prefix: 'v', line: 'ar myVar = <del>2</del>;'},
+        second: {
+          prefix: 'v',
+          line: 'ar myVar<ins>iable</ins> = <ins>3</ins>;'
+        }
+      }, result);
+    });
+  });
+});
diff --git a/test/side-by-side-printer-tests.js b/test/side-by-side-printer-tests.js
index c0d71cb..b7cc190 100644
--- a/test/side-by-side-printer-tests.js
+++ b/test/side-by-side-printer-tests.js
@@ -247,4 +247,48 @@ describe('SideBySidePrinter', function() {
       assert.equal(expected, html);
     });
   });
+
+  describe('processLines', function() {
+    it('should process file lines', function() {
+      var oldLines = [{
+        content: '-test',
+        type: 'd2h-del',
+        oldNumber: 1,
+        newNumber: null
+      }];
+
+      var newLines = [{
+        content: '+test1r',
+        type: 'd2h-ins',
+        oldNumber: null,
+        newNumber: 1
+      }];
+
+      var sideBySidePrinter = new SideBySidePrinter({matching: 'lines'});
+      var html = sideBySidePrinter.processLines(oldLines, newLines);
+      var expectedLeft =
+        '<tr>\n' +
+        '    <td class="d2h-code-side-linenumber d2h-del">1</td>\n' +
+        '    <td class="d2h-del">' +
+        '      <div class="d2h-code-side-line d2h-del">' +
+        '<span class="d2h-code-line-prefix">-</span>' +
+        '<span class="d2h-code-line-ctn">test</span></div>' +
+        '    </td>\n' +
+        '  </tr>\n';
+
+      var expectedRight =
+        '<tr>\n' +
+        '    <td class="d2h-code-side-linenumber d2h-ins">1</td>\n' +
+        '    <td class="d2h-ins">' +
+        '      <div class="d2h-code-side-line d2h-ins">' +
+        '<span class="d2h-code-line-prefix">+</span>' +
+        '<span class="d2h-code-line-ctn">test1r</span>' +
+        '</div>' +
+        '    </td>\n' +
+        '  </tr>\n';
+
+      assert.equal(expectedLeft, html.left);
+      assert.equal(expectedRight, html.right);
+    });
+  });
 });