some tests refactoring and sep by type

spec/unit/config_spec.lua

@@ -0,0 +1,22 @@
+describe("unit.gopher.config", function()
+  it("can be required", function()
+    require "gopher.config"
+  end)
+
+  describe(".setup()", function()
+    local c = require "gopher.config"
+
+    it("returns defaults when gets empty table", function()
+      c.setup {}
+      assert.are.same(c.config.commands.go, "go")
+      assert.are.same(c.config.commands.gomodifytags, "gomodifytags")
+      assert.are.same(c.config.commands.gotests, "gotests")
+      assert.are.same(c.config.commands.impl, "impl")
+    end)
+
+    it("can set user opts", function()
+      c.setup { commands = { go = "custom_go" } }
+      assert.are.same(c.config.commands.go, "custom_go")
+    end)
+  end)
+end)

spec/unit/utils_spec.lua

@@ -0,0 +1,19 @@
+describe("gopher._utils", function()
+  it("can be requried", function()
+    require "gopher._utils"
+  end)
+
+  describe(".empty()", function()
+    local empty = require("gopher._utils").empty
+
+    it("with non-empty talbe", function()
+      local res = empty { first = "1", second = 2 }
+      assert.are.same(res, false)
+    end)
+
+    it("with empty talbe", function()
+      local res = empty {}
+      assert.are.same(res, true)
+    end)
+  end)
+end)