Add test for /backup

Closes getodk#1305

test/integration/api/backup.js

@@ -1,11 +1,37 @@
+const { omit } = require('ramda');
 const { testService } = require('../setup');
-
+const { httpZipResponseToFiles } = require('../../util/zip');
 
 describe('api: /backup', () => {
-  describe('POST', () => {
+  describe('POST', function () {
+    this.timeout(10000);
     it('should reject if the user cannot backup', testService((service) =>
       service.login('chelsea', (asChelsea) =>
         asChelsea.post('/v1/backup').expect(403))));
+
+    it('should return a valid zip file if the user can backup @slow', testService((service) =>
+      service.login('alice', (asAlice) =>
+        httpZipResponseToFiles(asAlice.post('/v1/backup').expect(200))
+          .then(res => {
+            const constantProps = ['filenames', 'keepalive', 'keys.json', 'toc.dat'];
+            res.should.have.properties(constantProps);
+
+            const datFiles = Object.keys(omit(constantProps, res));
+            datFiles.length.should.be.greaterThan(0);
+            datFiles.should.matchEvery(/\.dat\.gz$/);
+
+            res.should.only.have.keys(...constantProps, ...datFiles);
+
+            const keysJson = JSON.parse(res['keys.json']);
+            keysJson.should.only.have.keys('iv', 'local', 'privkey', 'pubkey', 'salt');
+            keysJson.iv.should.be.a.String();
+            keysJson.privkey.should.be.a.String();
+            keysJson.pubkey.should.be.a.String();
+            keysJson.salt.should.be.a.String();
+            keysJson.local.should.only.have.keys('key', 'ivs');
+            keysJson.local.key.should.be.a.String();
+            keysJson.local.ivs.should.only.have.keys('toc.dat', ...datFiles);
+          }))));
   });
 });