cmd/tailscale/cli: move earlier shell test to its own files

(I should've done this to start with.)

Updates tailscale/corp#7515

Change-Id: I7fb88cf95772790fd415ecf28fc52bde95507641
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

cmd/tailscale/cli/cli_test.go

@@ -11,7 +11,6 @@
 	"fmt"
 	"net/netip"
 	"reflect"
-	"runtime"
 	"strings"
 	"testing"
 
@@ -1157,50 +1156,3 @@ func TestUpWorthWarning(t *testing.T) {
 		t.Errorf("want false for other misc errors")
 	}
 }
-
-func TestServeConfigMutations(t *testing.T) {
-	// Stateful mutations, starting from an empty config.
-	type step struct {
-		command []string // serve args
-		reset   bool     // if true, reset all ServeConfig state
-		want    *ipn.ServeConfig
-		wantErr string
-		line    int // line number of addStep call, for error messages
-	}
-	var steps []step
-	add := func(s step) {
-		_, _, s.line, _ = runtime.Caller(1)
-		steps = append(steps, s)
-	}
-	add(step{reset: true})
-	add(step{
-		want: nil,
-	})
-	var current *ipn.ServeConfig
-	for i, st := range steps {
-		t.Logf("Executing step #%d (line %v) ... ", i, st.line)
-		if st.reset {
-			t.Logf("(resetting state)")
-			current = nil
-		}
-		newState, err := applyServeMutation(current, st.command)
-		var gotErr string
-		if err != nil {
-			gotErr = err.Error()
-		}
-		if gotErr != st.wantErr {
-			t.Fatalf("[%d] %v: got error %q, want %q", i, st.command, gotErr, st.wantErr)
-		}
-		if !reflect.DeepEqual(newState, st.want) {
-			t.Fatalf("[%d] %v: bad state. got:\n%s\n\nwant:\n%s\n",
-				i, st.command, asJSON(newState), asJSON(st.want))
-		}
-	}
-}
-
-func applyServeMutation(current *ipn.ServeConfig, command []string) (*ipn.ServeConfig, error) {
-	if len(command) == 0 {
-		return current, nil
-	}
-	panic("TODO") // in cli/serve.go, not here in tests
-}

cmd/tailscale/cli/serve.go

@@ -0,0 +1,14 @@
+// Copyright (c) 2022 Tailscale Inc & AUTHORS All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package cli
+
+import "tailscale.com/ipn"
+
+func applyServeMutation(current *ipn.ServeConfig, command []string) (*ipn.ServeConfig, error) {
+	if len(command) == 0 {
+		return current, nil
+	}
+	panic("TODO")
+}

cmd/tailscale/cli/serve_test.go

@@ -0,0 +1,53 @@
+// Copyright (c) 2022 Tailscale Inc & AUTHORS All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package cli
+
+import (
+	"reflect"
+	"runtime"
+	"testing"
+
+	"tailscale.com/ipn"
+)
+
+func TestServeConfigMutations(t *testing.T) {
+	// Stateful mutations, starting from an empty config.
+	type step struct {
+		command []string // serve args
+		reset   bool     // if true, reset all ServeConfig state
+		want    *ipn.ServeConfig
+		wantErr string
+		line    int // line number of addStep call, for error messages
+	}
+	var steps []step
+	add := func(s step) {
+		_, _, s.line, _ = runtime.Caller(1)
+		steps = append(steps, s)
+	}
+	add(step{reset: true})
+	add(step{
+		want: nil,
+	})
+	var current *ipn.ServeConfig
+	for i, st := range steps {
+		t.Logf("Executing step #%d (line %v) ... ", i, st.line)
+		if st.reset {
+			t.Logf("(resetting state)")
+			current = nil
+		}
+		newState, err := applyServeMutation(current, st.command)
+		var gotErr string
+		if err != nil {
+			gotErr = err.Error()
+		}
+		if gotErr != st.wantErr {
+			t.Fatalf("[%d] %v: got error %q, want %q", i, st.command, gotErr, st.wantErr)
+		}
+		if !reflect.DeepEqual(newState, st.want) {
+			t.Fatalf("[%d] %v: bad state. got:\n%s\n\nwant:\n%s\n",
+				i, st.command, asJSON(newState), asJSON(st.want))
+		}
+	}
+}