feat: make tests run in coroutine to support asynchronous testing (#426)

Author: idanarye

TESTS_README.md

@@ -125,3 +125,19 @@ To test this in your `~/.config/nvim` configuration, try the suggested file stru
 lua/example/module.lua
 lua/spec/example/module_spec.lua
 ```
+
+# Asynchronous testing
+
+Tests run in a coroutine, which can be yielded and resumed. This can be used to
+test code that uses asynchronous Neovim functionalities. For example, this can
+be done inside a test:
+
+```lua
+local co = coroutine.running()
+vim.defer_fn(function()
+  coroutine.resume(co)
+end, 1000)
+--The test will reach here immediately.
+coroutine.yield()
+--The test will only reach here after one second, when the deferred function runs.
+```

lua/plenary/busted.lua

@@ -218,9 +218,9 @@ mod.run = function(file)
   print("\n" .. HEADER)
   print("Testing: ", file)
 
-  local ok, msg = pcall(dofile, file)
+  local loaded, msg = loadfile(file)
 
-  if not ok then
+  if not loaded then
     print(HEADER)
     print "FAILED TO LOAD FILE"
     print(color_string("red", msg))
@@ -232,33 +232,37 @@ mod.run = function(file)
     end
   end
 
-  -- If nothing runs (empty file without top level describe)
-  if not results.pass then
-    if is_headless then
-      return vim.cmd "0cq"
-    else
-      return
+  coroutine.wrap(function()
+    loaded()
+
+    -- If nothing runs (empty file without top level describe)
+    if not results.pass then
+      if is_headless then
+        return vim.cmd "0cq"
+      else
+        return
+      end
     end
-  end
 
-  mod.format_results(results)
+    mod.format_results(results)
 
-  if #results.errs ~= 0 then
-    print("We had an unexpected error: ", vim.inspect(results.errs), vim.inspect(results))
-    if is_headless then
-      return vim.cmd "2cq"
-    end
-  elseif #results.fail > 0 then
-    print "Tests Failed. Exit: 1"
+    if #results.errs ~= 0 then
+      print("We had an unexpected error: ", vim.inspect(results.errs), vim.inspect(results))
+      if is_headless then
+        return vim.cmd "2cq"
+      end
+    elseif #results.fail > 0 then
+      print "Tests Failed. Exit: 1"
 
-    if is_headless then
-      return vim.cmd "1cq"
-    end
-  else
-    if is_headless then
-      return vim.cmd "0cq"
+      if is_headless then
+        return vim.cmd "1cq"
+      end
+    else
+      if is_headless then
+        return vim.cmd "0cq"
+      end
     end
-  end
+  end)()
 end
 
 return mod

tests/plenary/async_testing_spec.lua

@@ -0,0 +1,75 @@
+local Job = require "plenary.job"
+
+local Timing = {}
+
+function Timing:log(name)
+  self[name] = vim.loop.uptime()
+end
+
+function Timing:check(from, to, min_elapsed)
+  assert(self[from], "did not log " .. from)
+  assert(self[to], "did not log " .. to)
+  local elapsed = self[to] - self[from]
+  assert(
+    min_elapsed <= elapsed,
+    string.format("only took %s to get from %s to %s - expected at least %s", elapsed, from, to, min_elapsed)
+  )
+end
+
+describe("Async test", function()
+  it("can resume testing with vim.defer_fn", function()
+    local co = coroutine.running()
+    assert(co, "not running inside a coroutine")
+
+    local timing = setmetatable({}, { __index = Timing })
+
+    vim.defer_fn(function()
+      coroutine.resume(co)
+    end, 200)
+    timing:log "before"
+    coroutine.yield()
+    timing:log "after"
+    timing:check("before", "after", 0.1)
+  end)
+
+  it("can resume testing from job callback", function()
+    local co = coroutine.running()
+    assert(co, "not running inside a coroutine")
+
+    local timing = setmetatable({}, { __index = Timing })
+
+    Job:new({
+      command = "bash",
+      args = {
+        "-ce",
+        [[
+        sleep 0.2
+        echo hello
+        sleep 0.2
+        echo world
+        sleep 0.2
+        exit 42
+      ]],
+      },
+      on_stdout = function(_, data)
+        timing:log(data)
+      end,
+      on_exit = function(_, exit_status)
+        timing:log "exit"
+        --This is required so that the rest of the test will run in a proper context
+        vim.schedule(function()
+          coroutine.resume(co, exit_status)
+        end)
+      end,
+    }):start()
+    timing:log "job started"
+    local exit_status = coroutine.yield()
+    timing:log "job finished"
+    assert.are.equal(exit_status, 42)
+
+    timing:check("job started", "job finished", 0.3)
+    timing:check("job started", "hello", 0.1)
+    timing:check("hello", "world", 0.1)
+    timing:check("world", "job finished", 0.1)
+  end)
+end)