feat(adapter): define Adapter interface and FileSet

internal/secrets/envsub_test.go

@@ -0,0 +1,32 @@
+package secrets
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestSubstituteSimple(t *testing.T) {
+	lookup := func(k string) (string, bool) {
+		if k == "FOO" {
+			return "bar", true
+		}
+		return "", false
+	}
+	out, err := Substitute("hello ${FOO}", lookup)
+	assert.NoError(t, err)
+	assert.Equal(t, "hello bar", out)
+}
+
+func TestSubstituteMissingStrict(t *testing.T) {
+	lookup := func(k string) (string, bool) { return "", false }
+	_, err := Substitute("${MISSING}", lookup)
+	assert.Error(t, err)
+}
+
+func TestSubstituteEscaped(t *testing.T) {
+	lookup := func(k string) (string, bool) { return "should-not-see", true }
+	out, err := Substitute("$${LITERAL}", lookup)
+	assert.NoError(t, err)
+	assert.Equal(t, "${LITERAL}", out)
+}