add tag checkout test

pkg/integration/components/shell.go

@@ -136,6 +136,10 @@ func (self *Shell) EmptyCommit(message string) *Shell {
 	return self.RunCommand(fmt.Sprintf("git commit --allow-empty -m \"%s\"", message))
 }
 
+func (self *Shell) CreateLightweightTag(name string, ref string) *Shell {
+	return self.RunCommand(fmt.Sprintf("git tag %s %s", name, ref))
+}
+
 // convenience method for creating a file and adding it
 func (self *Shell) CreateFileAndAdd(fileName string, fileContents string) *Shell {
 	return self.

pkg/integration/tests/tag/checkout.go

@@ -0,0 +1,31 @@
+package tag
+
+import (
+	"github.com/jesseduffield/lazygit/pkg/config"
+	. "github.com/jesseduffield/lazygit/pkg/integration/components"
+)
+
+var Checkout = NewIntegrationTest(NewIntegrationTestArgs{
+	Description:  "Checkout a tag",
+	ExtraCmdArgs: "",
+	Skip:         false,
+	SetupConfig:  func(config *config.AppConfig) {},
+	SetupRepo: func(shell *Shell) {
+		shell.EmptyCommit("one")
+		shell.EmptyCommit("two")
+		shell.CreateLightweightTag("tag", "HEAD^")
+	},
+	Run: func(t *TestDriver, keys config.KeybindingConfig) {
+		t.Views().Tags().
+			Focus().
+			Lines(
+				Contains("tag").IsSelected(),
+			).
+			PressPrimaryAction() // checkout tag
+
+		t.Views().Branches().IsFocused().Lines(
+			Contains("HEAD detached at tag").IsSelected(),
+			Contains("master"),
+		)
+	},
+})

pkg/integration/tests/tests_gen.go

@@ -86,6 +86,7 @@ var tests = []*components.IntegrationTest{
 	sync.Pull,
 	sync.PullAndSetUpstream,
 	sync.RenameBranchAndPull,
+	tag.Checkout,
 	tag.CrudAnnotated,
 	tag.CrudLightweight,
 	undo.UndoCheckoutAndDrop,