diff --git a/flags/flags_test.go b/flags/flags_test.go
new file mode 100644
index 0000000..c1f959a
--- /dev/null
+++ b/flags/flags_test.go
@@ -0,0 +1,85 @@
+package flags
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+const (
+	CMD     = "TEST"
+	SUMMARY = "SUMMARY"
+)
+
+type options struct {
+	Descriptor Arg
+	Tags       Arg
+	Source     String
+	Write      Bool
+	Help       Bool
+}
+
+func initOpts() options {
+	return options{
+		Arg{"", "midfix file descriptor"},
+		Arg{"", "tags to add to new file"},
+		String{"--source", "-s", "", "path to source list. reads from stdin if omitted."},
+		Bool{"--write", "-w", false, "write sorted list back to --key file"},
+		Bool{"--help", "-h", false, "show help"},
+	}
+}
+
+func TestParseArgsInternal(t *testing.T) {
+	flags := []Flag{
+		&Arg{"", "midfix file descriptor"},
+		&Arg{"", "tags to add to new file"},
+		&String{"--source", "-s", "", "path to source list. reads from stdin if omitted."},
+		&Bool{"--write", "-w", false, "write sorted list back to --key file"},
+		&Bool{"--help", "-h", false, "show help"},
+	}
+	args := []string{"--source", "foo"}
+	parseArgsInternal(CMD, SUMMARY, args, initOpts(), flags)
+	assert.False(t, flags[0].IsSet())
+	assert.False(t, flags[0].IsHelp())
+	assert.True(t, flags[2].IsSet())
+	assert.True(t, flags[4].IsHelp())
+
+}
+
+// TODO: return errors from Help routines and print at top level, so I can test those cases
+func TestParseArgsString(t *testing.T) {
+	args := []string{"--source", "foo"}
+	opts := initOpts()
+	ParseArgs(CMD, SUMMARY, args, &opts)
+	assert.Equal(t, opts.Source.Val, "foo")
+}
+
+func TestParseArgs(t *testing.T) {
+	opts := initOpts()
+	cases := []struct {
+		name       string
+		args       []string
+		stringVal  *string
+		stringWant string
+		boolVal    *bool
+		boolWant   bool
+	}{
+		{"arg", []string{"bar"}, &opts.Descriptor.Val, "bar", nil, false},
+		{"arg arg", []string{"bar", "foo"}, &opts.Tags.Val, "foo", nil, false},
+		{"--bool", []string{"--write"}, nil, "", &opts.Write.Val, true},
+		{"arg --bool", []string{"foo", "--write"}, &opts.Descriptor.Val, "foo", &opts.Write.Val, true},
+		{"--flag val", []string{"--source", "foo"}, &opts.Source.Val, "foo", nil, false},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			ParseArgs(CMD, SUMMARY, tc.args, &opts)
+			if tc.boolVal != nil {
+				assert.True(t, *tc.boolVal)
+			}
+			if tc.stringVal != nil {
+				assert.Equal(t, *tc.stringVal, tc.stringWant)
+			}
+		})
+	}
+}