separate KDF (not a proper KDF for now)

src/kdf/test.rs

@@ -0,0 +1,26 @@
+use super::*;
+use crate::kdf::kdf::DERIVED_KEY_LEN;
+
+#[test]
+fn key_has_expected_length() {
+    assert_eq!(DERIVED_KEY_LEN, 24);
+
+    let key = derive_file_key("test password");
+    assert_eq!(key.len(), DERIVED_KEY_LEN);
+}
+
+#[test]
+fn same_password_same_key() {
+    let a = derive_file_key("correct horse battery staple");
+    let b = derive_file_key("correct horse battery staple");
+
+    assert_eq!(a, b);
+}
+
+#[test]
+fn different_passwords_produce_different_keys() {
+    let a = derive_file_key("password1");
+    let b = derive_file_key("password2");
+
+    assert_ne!(a, b);
+}