Fix a couple inconsistencies in `operator usage instances` command

command/operator/usage/instances/usage_instances.go

@@ -33,8 +33,10 @@ type cmd struct {
 
 func (c *cmd) init() {
 	c.flags = flag.NewFlagSet("", flag.ContinueOnError)
-	c.flags.BoolVar(&c.onlyBillable, "billable", false, "Display only billable service info.")
-	c.flags.BoolVar(&c.onlyConnect, "connect", false, "Display only Connect service info.")
+	c.flags.BoolVar(&c.onlyBillable, "billable", false, "Display only billable service info. "+
+		"Cannot be used with -connect.")
+	c.flags.BoolVar(&c.onlyConnect, "connect", false, "Display only Connect service info."+
+		"Cannot be used with -billable.")
 	c.flags.BoolVar(&c.allDatacenters, "all-datacenters", false, "Display service counts from "+
 		"all datacenters.")
 
@@ -54,6 +56,11 @@ func (c *cmd) Run(args []string) int {
 		return 1
 	}
 
+	if c.onlyBillable && c.onlyConnect {
+		c.UI.Error("Cannot specify both -billable and -connect flags")
+		return 1
+	}
+
 	// Create and test the HTTP client
 	client, err := c.http.APIClient()
 	if err != nil {
@@ -219,22 +226,22 @@ func (c *cmd) Help() string {
 const (
 	synopsis = "Display service instance usage information"
 	help     = `
-Usage: consul usage instances [options]
+Usage: consul operator usage instances [options]
 
   Retrieves usage information about the number of services registered in a given
   datacenter. By default, the datacenter of the local agent is queried.
 
   To retrieve the service usage data:
 
-      $ consul usage instances
+      $ consul operator usage instances
 
   To show only billable service instance counts:
 
-      $ consul usage instances -billable
+      $ consul operator usage instances -billable
 
   To show only connect service instance counts:
 
-      $ consul usage instances -connect
+      $ consul operator usage instances -connect
 
   For a full list of options and examples, please see the Consul documentation.
 `

command/operator/usage/instances/usage_instances_test.go

@@ -1,6 +1,7 @@
 package instances
 
 import (
+	"errors"
 	"testing"
 
 	"github.com/hashicorp/consul/agent"
@@ -36,15 +37,40 @@ func TestUsageInstancesCommand(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	ui := cli.NewMockUi()
-	c := New(ui)
-	args := []string{
-		"-http-addr=" + a.HTTPAddr(),
+	cases := []struct {
+		name      string
+		extraArgs []string
+		output    string
+		err       error
+	}{
+		{
+			name:   "basic output",
+			output: "Billable Service Instances Total: 2",
+		},
+		{
+			name:      "billable and connect flags together are invalid",
+			extraArgs: []string{"-billable", "-connect"},
+			err:       errors.New("Cannot specify both -billable and -connect"),
+		},
 	}
-	code := c.Run(args)
-	if code != 0 {
-		t.Fatalf("bad exit code %d: %s", code, ui.ErrorWriter.String())
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			ui := cli.NewMockUi()
+			c := New(ui)
+			args := []string{
+				"-http-addr=" + a.HTTPAddr(),
+			}
+			args = append(args, tc.extraArgs...)
+
+			code := c.Run(args)
+			if tc.err != nil {
+				require.Equal(t, 1, code)
+				require.Contains(t, ui.ErrorWriter.String(), tc.err.Error())
+			} else {
+				require.Equal(t, 0, code)
+				require.Contains(t, ui.OutputWriter.String(), tc.output)
+			}
+		})
 	}
-	output := ui.OutputWriter.String()
-	require.Contains(t, output, "Billable Service Instances Total: 2")
 }