Fix typo (dispatch --> commit)

docs/en/testing.md

@@ -138,7 +138,7 @@ describe('actions', () => {
     
     actions.getAllProducts({ commit, state })
     
-    expect(dispatch.args).to.deep.equal([
+    expect(commit.args).to.deep.equal([
       [ 'REQUEST_PRODUCTS' ],
       [ 'RECEIVE_PRODUCTS', { /* mocked response */ } ]
     ])