Add tests for FullBatchBackPressureHandler (#1251)

Author: loicrouchon

spring-cloud-aws-sqs/src/test/java/io/awspring/cloud/sqs/listener/FullBatchBackPressureHandlerTest.java

@@ -0,0 +1,39 @@
+package io.awspring.cloud.sqs.listener;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class FullBatchBackPressureHandlerTest {
+
+	private FullBatchBackPressureHandler handler;
+
+	private final int batchSize = 10;
+
+    @BeforeEach
+    void setUp() {
+        handler = FullBatchBackPressureHandler.builder()
+                .batchSize(batchSize)
+                .build();
+    }
+
+    @Test
+    void request_withExactBatchSize_shouldReturnBatchSize() throws InterruptedException {
+        assertThat(handler.request(batchSize)).isEqualTo(batchSize);
+    }
+
+    @Test
+    void request_withNonBatchSize_shouldReturnZero() throws InterruptedException {
+        int permits = handler.request(batchSize - 1);
+        assertThat(permits).isZero();
+        permits = handler.request(batchSize + 1);
+        assertThat(permits).isZero();
+    }
+
+    @Test
+    void requestBatch_shouldReturnBatchSize() throws InterruptedException {
+        assertThat(handler.requestBatch()).isEqualTo(batchSize);
+    }
+}
+