Created test for getPromotionByPromoId

src/test/java/com/nisum/ascend/promotions/controller/PromotionsControllerTest.java

 package com.nisum.ascend.promotions.controller;
 
 import com.nisum.ascend.promotions.dto.PromotionDto;
-import com.nisum.ascend.promotions.model.Promotion;
 import lombok.extern.slf4j.Slf4j;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
@@ -28,9 +27,15 @@ import static org.junit.jupiter.api.Assertions.*;
 class PromotionsControllerTest {
     @Autowired
     private WebTestClient webTestClient;
+
     @BeforeEach
     void setUp() {
     }
+
+    WebTestClient.ResponseSpec getPromotionWebClient(String promoId) {
+        return webTestClient.get().uri("/api/promos/" + promoId).exchange();
+    }
+
     @Test
     void getAllPromotions() {
         webTestClient.get().uri("http://localhost:8081/api/promos").exchange()
@@ -48,4 +53,13 @@ class PromotionsControllerTest {
                     });
                 });
     }
+
+    @Test
+    void getPromotionById() {
+        getPromotionWebClient("0003")
+                .expectStatus().isOk()
+                .expectHeader().contentType(MediaType.APPLICATION_JSON_VALUE)
+                .expectBody()
+                .jsonPath("promotionId", "0003");
+    }
 }
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