Add contextLines as an option. (#6)

Author: ferrannp

__tests__/__snapshots__/snapshotDiff.test.js.snap

@@ -38,6 +38,25 @@ exports[`can expand diff 1`] = `
       script"
 `;
 
+exports[`can use contextLines on diff 1`] = `
+"- First value
++ Second value
+
+  
+      some
+      some
+      some
+      some
+      some
+      some
+      some
+      not
++     so
+      very
+      long
+      script"
+`;
+
 exports[`collapses diffs and strips ansi by default 1`] = `
 "- First value
 + Second value

__tests__/snapshotDiff.test.js

@@ -128,6 +128,10 @@ test('can colorize diff', () => {
   expect(snapshotDiff(a, b, {colors: true})).toMatchSnapshot();
 });
 
+test('can use contextLines on diff', () => {
+  expect(snapshotDiff(a, b, {contextLines: 0})).toMatchSnapshot();
+});
+
 test('diffs short strings', () => {
   const x = `
   abcx

src/index.js

@@ -8,12 +8,14 @@ const reactElement = Symbol.for('react.element');
 
 type Options = {
   expand?: boolean,
-  colors?: boolean
+  colors?: boolean,
+  contextLines?: number,
 };
 
 const defaultOptions = {
   expand: false,
-  colors: false
+  colors: false,
+  contextLines: -1, // Forces to use default from Jest
 };
 
 const snapshotDiff = (
@@ -42,6 +44,7 @@ const isReactComponent = valueA => valueA && valueA.$$typeof === reactElement;
 function diffStrings(valueA, valueB, options) {
   return diff(valueA, valueB, {
     expand: options.expand,
+    contextLines: options.contextLines,
     aAnnotation: 'First value',
     bAnnotation: 'Second value'
   });
@@ -55,6 +58,7 @@ function diffReactComponents(valueA, valueB, options) {
 
   return diff(reactValueA, reactValueB, {
     expand: options.expand,
+    contextLines: options.contextLines,
     aAnnotation: prettyFormat(valueA, prettyFormatOptions),
     bAnnotation: prettyFormat(valueB, prettyFormatOptions)
   });