Add state database toJSON() test.

test/src/coreutils/statedb.spec.ts

@@ -8,7 +8,7 @@ import {
 } from '@jupyterlab/coreutils';
 
 import {
-  PromiseDelegate
+  PromiseDelegate, ReadonlyJSONObject
 } from '@phosphor/coreutils';
 
 
@@ -236,4 +236,30 @@ describe('StateDB', () => {
 
   });
 
+  describe('#toJSON()', () => {
+
+    it('return the full contents of a state database', done => {
+      let { localStorage } = window;
+
+      let db = new StateDB({ namespace: 'test-namespace' });
+      let contents: ReadonlyJSONObject = {
+        abc: 'def',
+        ghi: 'jkl',
+        mno: 1,
+        pqr: {
+          foo: { bar: { baz: 'qux' } }
+        }
+      };
+
+      expect(localStorage.length).to.be(0);
+      Promise.all(Object.keys(contents).map(key => db.save(key, contents[key])))
+        .then(() => db.toJSON())
+        .then(serialized => { expect(serialized).to.eql(contents); })
+        .then(() => db.clear())
+        .then(done)
+        .catch(done);
+    });
+
+  });
+
 });