message: Improve coverage of from_container tests
diff: @@ -65,7 +65,9 @@ SCENARIO("container sources stream their input values") {
  THEN("the observer receives the values from the container in order") {
  auto xs = ivec{1, 2, 3, 4, 5, 6, 7};
  auto snk = flow::make_passive_observer<int>();
  - ctx->make_observable().from_container(xs).subscribe(snk->as_observer());
  + ctx->make_observable()
  + .from_container(std::move(xs))
  + .subscribe(snk->as_observer());
  CHECK_EQ(snk->state, flow::observer_state::subscribed);
  CHECK(snk->buf.empty());
  if (CHECK(snk->sub)) {
  @@ -79,6 +81,19 @@ SCENARIO("container sources stream their input values") {
  }
  }
  }
  + WHEN("combining it with with a step that limits the amount of items") {
  + THEN("the observer receives the defined subset of values") {
  + auto xs = iota_vec(713);
  + auto snk = flow::make_passive_observer<int>();
  + auto res = ivec{};
  + ctx->make_observable()
  + .from_container(std::move(xs))
  + .take(678)
  + .for_each([&res](int val) { res.push_back(val); });
  + ctx->run();
  + CHECK_EQ(res, iota_vec(678));
  + }
  + }
  }
  }
  