Retry exponential backoff #775 (#829)

* Spatial partition

* Retry with exponential backoff

* retry exponential backoff

* branch error

retry/src/test/java/com/iluwatar/retry/RetryExponentialBackoffTest.java

@@ -0,0 +1,115 @@
+/*
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2014-2016 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package com.iluwatar.retry;
+
+import org.junit.jupiter.api.Test;
+import static org.hamcrest.CoreMatchers.hasItem;
+import static org.hamcrest.CoreMatchers.is;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+/**
+ * Unit tests for {@link Retry}.
+ *
+ * @author George Aristy (george.aristy@gmail.com)
+ */
+public class RetryExponentialBackoffTest {
+    /**
+     * Should contain all errors thrown.
+     */
+  @Test
+  public void errors() throws Exception {
+    final BusinessException e = new BusinessException("unhandled");
+    final RetryExponentialBackoff<String> retry = new RetryExponentialBackoff<>(
+        () -> { 
+          throw e; 
+        },
+        2,
+        0
+    );
+    try {
+      retry.perform();
+    } catch (BusinessException ex) {
+      //ignore
+    }
+
+    assertThat(
+        retry.errors(),
+        hasItem(e)
+    );
+  }
+
+    /**
+     * No exceptions will be ignored, hence final number of attempts should be 1 even if we're asking
+     * it to attempt twice.
+     */
+  @Test
+  public void attempts() {
+    final BusinessException e = new BusinessException("unhandled");
+    final RetryExponentialBackoff<String> retry = new RetryExponentialBackoff<>(
+        () -> { 
+          throw e; 
+        },
+        2,
+        0
+    );
+    try {
+      retry.perform();
+    } catch (BusinessException ex) {
+      //ignore
+    }
+
+    assertThat(
+        retry.attempts(),
+        is(1)
+    );
+  }
+
+    /**
+     * Final number of attempts should be equal to the number of attempts asked because we are
+     * asking it to ignore the exception that will be thrown.
+     */
+  @Test
+  public void ignore() throws Exception {
+    final BusinessException e = new CustomerNotFoundException("customer not found");
+    final RetryExponentialBackoff<String> retry = new RetryExponentialBackoff<>(
+        () -> { 
+          throw e; 
+        },
+        2,
+        0,
+        ex -> CustomerNotFoundException.class.isAssignableFrom(ex.getClass())
+    );
+    try {
+      retry.perform();
+    } catch (BusinessException ex) {
+      //ignore
+    }
+
+    assertThat(
+        retry.attempts(),
+        is(2)
+    );
+  }
+}