add tests

Author: orevron

src/compute-lines.ts

@@ -140,7 +140,7 @@ const computeLineInformation = (
   newString: string,
   disableWordDiff: boolean = false,
   compareMethod: string = DiffMethod.CHARS,
-  linesOffset: number
+  linesOffset: number = 0,
 ): ComputedLineInformation => {
   const diffArray = diff.diffLines(
     oldString.trimRight(),

src/index.tsx

@@ -85,7 +85,7 @@ class DiffViewer extends React.Component<ReactDiffViewerProps, ReactDiffViewerSt
     extraLinesSurroundingDiff: 3,
     showDiffOnly: true,
     useDarkTheme: false,
-    linesOffset: 0
+    linesOffset: 0,
   };
 
   public static propTypes = {
@@ -109,7 +109,7 @@ class DiffViewer extends React.Component<ReactDiffViewerProps, ReactDiffViewerSt
       PropTypes.string,
       PropTypes.element,
     ]),
-    linesOffset: PropTypes.number
+    linesOffset: PropTypes.number,
   };
 
   public constructor(props: ReactDiffViewerProps) {
@@ -451,7 +451,7 @@ class DiffViewer extends React.Component<ReactDiffViewerProps, ReactDiffViewerSt
       newValue,
       disableWordDiff,
       compareMethod,
-      linesOffset
+      linesOffset,
     );
     const extraLines = this.props.extraLinesSurroundingDiff < 0
       ? 0

test/compute-lines-test.ts

@@ -374,4 +374,40 @@ Also this info`;
         ],
       });
   });
+
+  it('Should start line counting from offset', (): void => {
+    const oldCode = 'Hello World';
+    const newCode = `My Updated Name
+Also this info`;
+
+    expect(computeLineInformation(oldCode, newCode, true, DiffMethod.WORDS, 5))
+      .toMatchObject({
+        lineInformation: [
+          {
+            right: {
+              lineNumber: 6,
+              type: 1,
+              value: 'My Updated Name',
+            },
+            left: {
+              lineNumber: 6,
+              type: 2,
+              value: 'Hello World',
+            },
+          },
+          {
+            right: {
+              lineNumber: 7,
+              type: 1,
+              value: 'Also this info',
+            },
+            left: {},
+          },
+        ],
+        diffLines: [
+          0,
+          2,
+        ],
+      });
+  });
 });