WalletSetPasswordControllerTest: test key derivation time

Ensure key derivation time with `WalletSetPasswordController#SCRYPT_PARAMETERS`
isn't inordinately slow. This is in preparation for some forthcoming changes to
the progress meter in `WalletSetPasswordController`.

wallettemplate/src/test/java/wallettemplate/WalletSetPasswordControllerTest.java

@@ -0,0 +1,54 @@
+/*
+ * Copyright by the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package wallettemplate;
+
+import org.bitcoinj.crypto.KeyCrypterScrypt;
+import org.junit.jupiter.api.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.time.Duration;
+
+import static org.junit.jupiter.api.Assertions.assertTrue;
+import static wallettemplate.WalletSetPasswordController.SCRYPT_PARAMETERS;
+
+public class WalletSetPasswordControllerTest {
+    private static final Logger log = LoggerFactory.getLogger(WalletSetPasswordController.class);
+
+    /**
+     * Ensure key derivation time with {@link WalletSetPasswordController#SCRYPT_PARAMETERS} isn't inordinately slow.
+     */
+    @Test
+    void keyDerivationIsNotTooSlow() {
+        // Measure key derivation time with our
+        Duration duration = measureKeyDerivationTime();
+        assertTrue(duration.compareTo(Duration.ofSeconds(30)) < 0, "Key derivation took too long.");
+    }
+
+    /**
+     * Measure key derivation time
+     * @return measured duration
+     */
+    private static Duration measureKeyDerivationTime() {
+        log.info("Doing background test key derivation");
+        KeyCrypterScrypt scrypt = new KeyCrypterScrypt(SCRYPT_PARAMETERS);
+        long start = System.currentTimeMillis();
+        scrypt.deriveKey("test password");
+        long msec = System.currentTimeMillis() - start;
+        log.info("Background test key derivation took {}msec", msec);
+        return Duration.ofMillis(msec);
+    }
+}