feat: Provide per test "context" that is shared with "beforeEach"

[jamestalmage]

Right now beforeEach has limited utility in concurrent tests. The following won't work because both tests manipulate a shared variable and run concurrently:

var obj;

test.beforeEach(t => {
  obj = // ... some verbose setup code.  
  t.end();
});

test('test1', t => {
  // tests with side-affects  on `obj` 

  // sometime later
  t.end();
});

test('test2', t => {
  // tests with side-affects  on `obj` 

  // sometime later
  t.end();
});

To address this, I think it would be good to provide a this reference that is shared between beforeEach and the individual test:

var globalCount = 1;

test.beforeEach(t => {
  this.count = globalCount;
  globalCount++;
  t.end();
});

test('test1', t => {
  t.plan(1);
  var self = this;
  setTimeout(() => t.is(self.count, 1));
});

test('test2', t => {
  t.plan(1);
  var self = this;
  setTimeout(() => t.is(self.count, 2));
});

The above is maybe not the best example and might fail since I doubt we are guaranteeing test instantiation order in a concurrent testing framework.

Another alternative might be to pass the context as an optional second arg:

var globalCount = 1;

test.beforeEach((t, ctx) => {
  ctx.count = globalCount;
  globalCount++;
  t.end();
});

test('test1', (t, ctx) => {
  t.plan(1);
  setTimeout(() => t.is(ctx.count, 1));
});

test('test2', (t, ctx) => {
  t.plan(1);
  setTimeout(() => t.is(ctx.count, 2));
});

This has the advantage of avoiding self reference verbosity.

[schnittstabil]

Doesn't t.context do the job?

[jamestalmage]

CRAP!
How did I miss that?!