add test to verify empty string is returned for last name when customer name is null

Author: AnirudhBhat

example/src/test/java/org/wordpress/android/fluxc/model/customer/WCCustomerMapperTest.kt

@@ -331,8 +331,21 @@ class WCCustomerMapperTest {
         val result = mapper.mapToModel(site, customerDTO)
 
         // then
-        with(result) {
-            assertEquals("lastname", lastName)
-        }
+        assertEquals("lastname", result.lastName)
+    }
+
+    @Test
+    fun `given customer name as null, then last name returns empty string`() {
+        // given
+        val siteId = 23
+        val site = SiteModel().apply { id = siteId }
+
+        val customerDTO = CustomerFromAnalyticsDTO(name = null)
+
+        // when
+        val result = mapper.mapToModel(site, customerDTO)
+
+        // then
+        assertEquals("", result.lastName)
     }
 }