diff --git a/cmd/spectre/main.go b/cmd/spectre/main.go
index da941f8..a399981 100644
--- a/cmd/spectre/main.go
+++ b/cmd/spectre/main.go
@@ -10,6 +10,15 @@ import (
 )
 
 func main() {
+	pw, err := doMain(os.Args[1:])
+	if err != nil {
+		fmt.Println(err)
+		return
+	}
+	fmt.Println(pw)
+}
+
+func doMain(args []string) (string, error) {
 	fs := flag.NewFlagSet("spectre", flag.ExitOnError)
 	fs.Usage = func() {
 		fmt.Fprintln(fs.Output(), "spectre [FLAGS] [site]")
@@ -30,11 +39,11 @@ func main() {
 		return
 	})
 
-	if err := fs.Parse(os.Args[1:]); err != nil {
-		panic(err)
+	if err := fs.Parse(args); err != nil {
+		return "", err
 	}
 	if err := checkEnv(fs); err != nil {
-		panic(err)
+		return "", err
 	}
 
 	if templateFlag == "" {
@@ -42,23 +51,45 @@ func main() {
 	}
 
 	if *usernameFlag == "" || *secretFlag == "" || fs.NArg() < 1 {
-		panic("username, secret, and site are required")
+		return "", requiredArgs{
+			missingUsername: *usernameFlag == "",
+			missingSecret:   *secretFlag == "",
+			missingSite:     fs.NArg() < 1,
+		}
 	}
 
 	s, err := spectre.New(*usernameFlag, *secretFlag, spectre.WithScoper(spectre.SimpleScoper{
 		Key: *scoperFlag,
 	}))
 	if err != nil {
-		panic(err)
+		return "", err
 	}
 
-	pw := s.Site(fs.Arg(0),
+	return s.Site(fs.Arg(0),
 		spectre.WithScope(scopeFlag),
 		spectre.WithTemplate(templateFlag),
 		spectre.WithCounter(*counterFlag),
-	)
+	), nil
+}
 
-	fmt.Println(pw)
+type requiredArgs struct {
+	missingUsername bool
+	missingSecret   bool
+	missingSite     bool
+}
+
+func (r requiredArgs) Error() string {
+	s := "--username, --secret, and <site-name> are required, missing: "
+	if r.missingUsername {
+		s += "\n- username"
+	}
+	if r.missingSecret {
+		s += "\n- secret"
+	}
+	if r.missingSite {
+		s += "\n- site name"
+	}
+	return s
 }
 
 func checkEnv(fs *flag.FlagSet) error {
diff --git a/cmd/spectre/main_test.go b/cmd/spectre/main_test.go
new file mode 100644
index 0000000..2f28f8d
--- /dev/null
+++ b/cmd/spectre/main_test.go
@@ -0,0 +1,76 @@
+package main
+
+import (
+	_ "embed"
+	"encoding/xml"
+	"fmt"
+	"testing"
+)
+
+// These are the exact same tests as spectre_test.go
+// These are here just to make sure the CLI is giving the same outputs
+func TestCLI(t *testing.T) {
+	var tests TestCases
+	if err := xml.Unmarshal(testsXML, &tests); err != nil {
+		t.Log("could not load test data")
+		t.FailNow()
+	}
+
+	dc := tests.Cases[0]
+	for _, tc := range tests.Cases[1:] {
+		t.Run(tc.ID, func(t *testing.T) {
+			user := def(dc.UserName, tc.UserName)
+			secret := def(dc.UserSecret, tc.UserSecret)
+			siteName := def(dc.SiteName, tc.SiteName)
+			template := def(dc.ResultType, tc.ResultType)
+			counter := def(dc.KeyCounter, tc.KeyCounter)
+			scope := def(dc.KeyPurpose, tc.KeyPurpose)
+
+			args := []string{
+				"--username", user,
+				"--secret", secret,
+				"--template", template,
+				"--counter", counter,
+				"--scope", scope,
+				siteName,
+			}
+			fmt.Println(args)
+
+			pw, err := doMain(args)
+			if err != nil {
+				t.Log(err)
+				t.FailNow()
+			}
+
+			if pw != tc.Result {
+				t.Log("passwords did not match")
+				t.Fail()
+			}
+		})
+	}
+}
+
+//go:embed spectre_tests.xml
+var testsXML []byte
+
+type TestCases struct {
+	Cases []TestCase `xml:"case"`
+}
+
+type TestCase struct {
+	ID         string `xml:"id,attr"`
+	UserName   string `xml:"userName"`
+	UserSecret string `xml:"userSecret"`
+	SiteName   string `xml:"siteName"`
+	ResultType string `xml:"resultType"`
+	KeyCounter string `xml:"keyCounter"`
+	KeyPurpose string `xml:"keyPurpose"`
+	Result     string `xml:"result"`
+}
+
+func def(def, alt string) string {
+	if alt != "" {
+		return alt
+	}
+	return def
+}
diff --git a/spectre_tests.xml b/cmd/spectre/spectre_tests.xml
similarity index 100%
rename from spectre_tests.xml
rename to cmd/spectre/spectre_tests.xml
diff --git a/spectre_test.go b/spectre_test.go
index 3bfcec8..cf888ad 100644
--- a/spectre_test.go
+++ b/spectre_test.go
@@ -84,7 +84,7 @@ func Example_second() {
 	// Output: Ig^JIcxD!*)TbefJBi6-
 }
 
-//go:embed spectre_tests.xml
+//go:embed cmd/spectre/spectre_tests.xml
 var testsXML []byte
 
 type TestCases struct {