test(iferr): add test

chore(ci): install go, and go bins for tests

spec/testutils.lua

@@ -12,7 +12,32 @@ function testutils.eq(a, b)
   return MiniTest.expect.equality(a, b)
 end
 
--- TODO: continue with writing fixtures helpers
--- https://github.com/olexsmir/gopher.nvim/pull/71/files
+---@return string
+function testutils.tmpfile()
+  return vim.fn.tempname() .. ".go"
+end
+
+---@param path string
+---@return string
+function testutils.readfile(path)
+  return vim.fn.join(vim.fn.readfile(path), "\n")
+end
+
+testutils.fixtures = {}
+
+---@param fixture string
+---@return {input: string, output: string}
+function testutils.fixtures.read(fixture)
+  return {
+    input = testutils.readfile(fixtures_dir .. fixture .. "_input.go"),
+    output = testutils.readfile(fixtures_dir .. fixture .. "_output.go"),
+  }
+end
+
+---@param fpath string
+---@param fixture string
+function testutils.fixtures.write(fpath, fixture)
+  vim.fn.writefile(vim.split(fixture, "\n"), fpath)
+end
 
 return testutils