Improve testing for supervisor composition modules

This PR cleans up testing for supervisor compose modules. It also fixes broken
tests for application manager and removes a lot of dependencies for those tests
on DB and other unnecessary mocks. There are probably a lot of cases that tests
are missing but this should make writing new tests a lot easier.

This PR also creates a new mock dockerode (mockerode) module that should make it
easier to test operations that interact with the engine. All references
to the old mock-dockerode have not yet been removed but that should come
soon in another PR

List of squashed commits:
- Add tests for network create/remove
- Move compose service tests to test/src/compose and reorganize test descriptions
- Add support for image creation to mockerode
- Add additional tests for compose volumes
- Update mockerode so unimplemented fake methods throw. This is to ensure
  tests using mockerode fail if an unimplemented method is used
- Update tests for volume-manager with mockerode
- Update tests for compose/images
- Simplify tests using mockerode
- Clean up compose/app tests
- Create application manager tests

Change-type: minor

test/lib/db-helper.ts

@@ -0,0 +1,82 @@
+import * as constants from '../../src/lib/constants';
+import * as db from '../../src/db';
+import * as sinon from 'sinon';
+
+import rewire = require('rewire');
+
+// Creates a test database and returns a query builder
+export async function createDB() {
+	const oldDatabasePath = process.env.DATABASE_PATH;
+
+	// for testing we use an in memory database
+	process.env.DATABASE_PATH = ':memory:';
+
+	// @ts-ignore
+	constants.databasePath = process.env.DATABASE_PATH;
+
+	// Cleanup the module cache in order to have it reloaded in the local context
+	delete require.cache[require.resolve('../../src/db')];
+	const testDb = rewire('../../src/db');
+
+	// Initialize the database module
+	await testDb.initialized;
+
+	// Get the knex instance to allow queries to the db
+	const knex = testDb.__get__('knex');
+	const { models } = testDb;
+
+	// This is hacky but haven't found another way to do it,
+	// stubbing the db methods here ensures the module under test
+	// is using the database we want
+	sinon.stub(db, 'models').callsFake(models);
+	sinon.stub(db, 'upsertModel').callsFake(testDb.upsertModel);
+
+	return {
+		// Returns a query builder instance for the given
+		// table in order perform data operations
+		models,
+
+		// Resets the database to initial value post
+		// migrations
+		async reset() {
+			// Reset the contents of the db
+			await testDb.transaction(async (trx: any) => {
+				const result = await trx.raw(`
+			SELECT name, sql
+			FROM sqlite_master
+			WHERE type='table'`);
+				for (const r of result) {
+					// We don't run the migrations again
+					if (r.name !== 'knex_migrations') {
+						await trx.raw(`DELETE FROM ${r.name}`);
+					}
+				}
+
+				// The supervisor expects this value to already have
+				// been pre-populated
+				await trx('deviceConfig').insert({ targetValues: '{}' });
+			});
+
+			// Reset stub call history
+			(db.models as sinon.SinonStub).resetHistory();
+			(db.upsertModel as sinon.SinonStub).resetHistory();
+		},
+
+		// Destroys the in-memory database and resets environment
+		async destroy() {
+			await knex.destroy();
+
+			// Restore the old datbase path
+			process.env.DATABASE_PATH = oldDatabasePath;
+
+			// Restore stubs
+			(db.models as sinon.SinonStub).restore();
+			(db.upsertModel as sinon.SinonStub).restore();
+
+			// @ts-ignore
+			constants.databasePath = process.env.DATABASE_PATH;
+		},
+	};
+}
+
+export type TestDatabase = UnwrappedPromise<ReturnType<typeof createDB>>;