Re-arrange OAuth service tests

Move the tests for fetching and persistence of tokens from/to storage
into the `describe('#tokenGetter', ...` block since this is the method
called from outside the service that initiates the fetching /
persistence.

Also reword a couple of the test cases to be clearer now that the OAuth
service now handles fetching tokens using methods other than exchanging
grant tokens.

src/sidebar/test/oauth-auth-test.js

@@ -169,7 +169,7 @@ describe('sidebar.oauth-auth', function () {
   });
 
   describe('#tokenGetter', function () {
-    it('should request an access token if a grant token was provided', function () {
+    it('exchanges the grant token for an access token if provided', function () {
       return auth.tokenGetter().then(function (token) {
         var expectedBody =
           'assertion=a.jwt.token' +
@@ -256,7 +256,7 @@ describe('sidebar.oauth-auth', function () {
       return Promise.all(tokens);
     });
 
-    it('should return null if no grant token was provided', function () {
+    it('should not attempt to exchange a grant token if none was provided', function () {
       fakeSettings.services = [{ authority: 'publisher.org' }];
       return auth.tokenGetter().then(function (token) {
         assert.notCalled(fakeHttp.post);
@@ -352,14 +352,10 @@ describe('sidebar.oauth-auth', function () {
         });
       });
     });
-  });
 
-  describe('persistence of tokens to storage', () => {
-    beforeEach(() => {
+    it('persists tokens retrieved via auth code exchanges to storage', () => {
       fakeSettings.services = [];
-    });
 
-    it('persists tokens retrieved via auth code exchanges to storage', () => {
       return login().then(() => {
         return auth.tokenGetter();
       }).then(() => {
@@ -372,6 +368,8 @@ describe('sidebar.oauth-auth', function () {
     });
 
     it('persists refreshed tokens to storage', () => {
+      fakeSettings.services = [];
+
       // 1. Perform initial token exchange.
       return login().then(() => {
         return auth.tokenGetter();
@@ -398,7 +396,9 @@ describe('sidebar.oauth-auth', function () {
       });
     });
 
-    it('loads and uses tokens from storage', () => {
+    it('fetches and returns tokens from storage', () => {
+      fakeSettings.services = [];
+
       fakeLocalStorage.getObject.withArgs(TOKEN_KEY).returns({
         accessToken: 'foo',
         refreshToken: 'bar',
@@ -410,7 +410,9 @@ describe('sidebar.oauth-auth', function () {
       });
     });
 
-    it('refreshes the token if it expired after loading from storage', () => {
+    it('refreshes expired tokens loaded from storage', () => {
+      fakeSettings.services = [];
+
       // Store an expired access token.
       clock.tick(200);
       fakeLocalStorage.getObject.withArgs(TOKEN_KEY).returns({
@@ -458,6 +460,7 @@ describe('sidebar.oauth-auth', function () {
     }].forEach(({ when, data }) => {
       context(when, () => {
         it('ignores invalid tokens in storage', () => {
+          fakeSettings.services = [];
           fakeLocalStorage.getObject.withArgs('foo').returns(data);
           return auth.tokenGetter().then((token) => {
             assert.equal(token, null);
@@ -465,8 +468,13 @@ describe('sidebar.oauth-auth', function () {
         });
       });
     });
+  });
 
   context('when another client instance saves new tokens', () => {
+    beforeEach(() => {
+      fakeSettings.services = [];
+    });
+
     function notifyStoredTokenChange() {
       // Trigger "storage" event as if another client refreshed the token.
       var storageEvent = new Event('storage');
@@ -504,10 +512,8 @@ describe('sidebar.oauth-auth', function () {
       assert.called(onTokenChange);
     });
   });
-  });
 
   describe('#login', () => {
-
     beforeEach(() => {
       // login() is only currently used when using the public
       // Hypothesis service.