Adding new Superuser contract with test (#952)

* Adding new Superuser contract + tests

test/ownership/Superuser.test.js

@@ -0,0 +1,62 @@
+import expectThrow from '../helpers/expectThrow';
+import expectEvent from '../helpers/expectEvent';
+
+const Superuser = artifacts.require('Superuser');
+
+require('chai')
+  .use(require('chai-as-promised'))
+  .should();
+
+contract('Superuser', function (accounts) {
+  const [
+    firstOwner,
+    newSuperuser,
+    newOwner,
+    anyone,
+  ] = accounts;
+
+  before(async function () {
+    this.superuser = await Superuser.new();
+  });
+
+  context('in normal conditions', () => {
+    it('should set the owner as the default superuser', async function () {
+      const ownerIsSuperuser = await this.superuser.isSuperuser(firstOwner);
+      ownerIsSuperuser.should.be.equal(true);
+    });
+
+    it('should change superuser after transferring', async function () {
+      await this.superuser.transferSuperuser(newSuperuser, { from: firstOwner });
+      
+      const ownerIsSuperuser = await this.superuser.isSuperuser(firstOwner);
+      ownerIsSuperuser.should.be.equal(false);
+
+      const address1IsSuperuser = await this.superuser.isSuperuser(newSuperuser);
+      address1IsSuperuser.should.be.equal(true);
+    });
+
+    it('should change owner after transferring', async function () {
+      await expectEvent.inTransaction(
+        this.superuser.transferOwnership(newOwner, { from: newSuperuser }),
+        'OwnershipTransferred'
+      );
+
+      const currentOwner = await this.superuser.owner();
+      currentOwner.should.be.equal(newOwner);
+    });
+  });
+
+  context('in adversarial conditions', () => {
+    it('should prevent non-superusers from transfering the superuser role', async function () {
+      await expectThrow(
+        this.superuser.transferSuperuser(newOwner, { from: anyone })
+      );
+    });
+
+    it('should prevent non-superusers from setting a new owner', async function () {
+      await expectThrow(
+        this.superuser.transferOwnership(newOwner, { from: anyone })
+      );
+    });
+  });
+});