Tests

[lifeart]

Add tests for:

• [x] VM (attribute updated, property updated, textContent updated, class merged) https://github.com/lifeart/glimmer-next/pull/37
• [ ] component, helper, modifier helpers tests https://github.com/lifeart/glimmer-next/pull/85
• [ ] each inside each
• [x] DOM builders (we could create known html tags)
• [x] Runtime (tbd)
• [x] Cell (cell instances should work as primitives in templates (boolean,number,string)), could be used as attribute/property and condition (for if) and remains reactive https://github.com/lifeart/glimmer-next/pull/34
• [x] MergedCell should work as primitives in templates (boolean,number,string)), could be used as attribute/property and condition (for if) and remains reactive https://github.com/lifeart/glimmer-next/pull/34
• [x] effect (function should re-execute if related fields changes) https://github.com/lifeart/glimmer-next/pull/32
• [x] modifier (it should run before document in dom and execute destructors if component is removed) https://github.com/lifeart/glimmer-next/pull/33
• [x] formula (tbd) https://github.com/lifeart/glimmer-next/pull/34
• [x] slots (if no yeild - no slots, default slot tests and multiple slots tests) https://github.com/lifeart/glimmer-next/pull/31
• [x] conditional slots (slot with same name could be in different if conditions, we need to check how it's working) https://github.com/lifeart/glimmer-next/pull/35
• [x] @args (field types should match inputs - primitives, functions) https://github.com/lifeart/glimmer-next/pull/36
• [x] class-based component (tbd) https://github.com/lifeart/glimmer-next/pull/36
• [x] template-only component https://github.com/lifeart/glimmer-next/pull/36
• [ ] function based component (tbd)
• [ ] components with root node (tbd)
• [ ] components without root node (tbd)
• [x] if opcode
• [x] each opcode (list is rendered, and keeping in sync ordering of items)
• [x] hbs compiler (tbd)
• [ ] in-element should remove anchor comment if updated/removed (now it's appending to old one)

[lifeart]