Update the developer docs with more info about creating tests

DEVELOPER.md

@@ -80,7 +80,46 @@ You can link (or simply copy/paste) this directory into your project and test Ty
 
 ## Running Tests Locally
 
-Setup your environment configuration by copying `ormconfig.json.dist` into `ormconfig.json` and 
+It would be greatly appreciated if PRs that change code come with appropriate tests.
+
+To create a test for a specific issue opened on github, create a file: `test/github-issues/<num>/issue-<num>.ts` where
+`<num>` is the corresponding github issue. For example, if you were creating a PR to fix github issue #363, you'd 
+create `test/github-issues/363/issue-363.ts`.
+
+Most tests will benefit from using this template as a starting point:
+
+```ts
+import "reflect-metadata";
+import {createTestingConnections, closeTestingConnections, reloadTestingDatabases} from "../../utils/test-utils";
+import {Connection} from "../../../src/connection/Connection";
+import {expect} from "chai";
+
+describe("github issues > #<issue number> <issue title>", () => {
+
+    let connections: Connection[];
+    before(async () => connections = await createTestingConnections({
+        entities: [__dirname + "/entity/*{.js,.ts}"],
+        schemaCreate: true,
+        dropSchemaOnConnection: true,
+    }));
+    beforeEach(() => reloadTestingDatabases(connections));
+    after(() => closeTestingConnections(connections));
+
+    it("should <put a detailed description of what it should do here>", () => Promise.all(connections.map(async connection => {
+
+       // tests go here
+
+    })));
+    
+    // you can add additional tests if needed
+
+});
+```
+
+If you place entities in `./entity/<entity-name>.ts` relative to your `issue-<num>.ts` file, 
+they will automatically be loaded.
+
+To run the tests, setup your environment configuration by copying `ormconfig.json.dist` into `ormconfig.json` and 
 replacing parameters with your own.
 
 Then run tests:
@@ -92,6 +131,15 @@ npm test
 You should execute test suites before submitting a PR to github.
 All the tests are executed on our Continuous Integration infrastructure and a PR could only be merged once the tests pass.
 
+>**Hint:** you can use the `--grep` flag to pass a Regex to `gulp-mocha`. Only the tests have have `describe`/`it` 
+>statements that match the Regex will be run. For example:
+>
+>```shell
+>npm test -- --grep="github issues > #363"
+>```
+>
+>This is useful when trying to get a specific test or subset of tests to pass.
+
 ## Using Docker 
 
 To run your tests you need dbms installed on your machine. Alternatively, you can use docker 

gulpfile.ts

@@ -19,6 +19,7 @@ const sourcemaps = require("gulp-sourcemaps");
 const istanbul = require("gulp-istanbul");
 const remapIstanbul = require("remap-istanbul/lib/gulpRemapIstanbul");
 const ts = require("gulp-typescript");
+const args = require('yargs').argv;
 
 @Gulpclass()
 export class Gulpfile {
@@ -297,6 +298,7 @@ export class Gulpfile {
         return gulp.src(["./build/compiled/test/**/*.js"])
             .pipe(mocha({
                 bail: true,
+                grep: !!args.grep ? new RegExp(args.grep) : undefined,
                 timeout: 15000
             }))
             .pipe(istanbul.writeReports());