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This is an example taken directly from busted documentation:

    local t = {
      greet = function(msg) print(msg) end
    }

    stub(t, "greet")

    t.greet("Hey!") -- DOES NOT print 'Hey!'
    assert.stub(t.greet).was.called_with("Hey!")

Lua LS gives the following error on the assertion line:

Diagnostics:                                                        
Cannot assign `function` to parameter `luassert.spy`.               
- `function` cannot match `luassert.spy`                            
- Type `function` cannot match `luassert.spy` [param-type-mismatch]

I'm not sure how to fix this. Changing the param in the meta file to luassert.spy|function may be a workaround but would not be accurate. The problem is that t.greet is already a luassert.spy object but the language server incorrectly assumes that it is a function. The object is modified in-place and after the call:

local s = stub(t, "greet")

t.greet is no longer a function but a callable table. Both s and t.greet point to the same object (of type luassert.spy). It would be best if the language server could figure this out.

luassert assertions support a trailing message parameter, but the annotations don't allow for that. For example, this code works (producing the custom error on failure) but the string is highlighted with the LLS warning "This function expects a maximum of 1 argument(s) but instead it is receiving 2. Lua Diagnostics.(redundant-parameter)"

    local crumb = self.engine:poll()
    assert.is_nil(crumb, 'Expected nil end of event queue')