add validation for items size

Author: quiteeasy

constructorio-client/src/main/java/io/constructor/client/ConstructorIO.java

@@ -1812,6 +1812,10 @@ public String recommendationsAsJSON(RecommendationsRequest req, UserInfo userInf
             }
 
             if (StringUtils.isNotBlank(req.getVariationId())) {
+                if (req.getItemIds() == null || req.getItemIds().size() != 1) {
+                    throw new IllegalArgumentException(
+                            "variationId requires exactly one itemId to be specified");
+                }
                 url =
                         url.newBuilder()
                                 .addQueryParameter("variation_id", req.getVariationId())

constructorio-client/src/test/java/io/constructor/client/ConstructorIORecommendationsTest.java

@@ -37,10 +37,35 @@ public void getRecommendationsShouldReturnAResultWithItemIdAndVariationId() thro
         request.setItemIds(Arrays.asList("power_drill"));
         request.setVariationId("power_drill_variation");
         RecommendationsResponse response = constructor.recommendations(request, userInfo);
-        assertTrue("recommendation results exist", response.getResponse().getResults().size() >= 0);
+        assertTrue("recommendation results exist", response.getResponse().getResults().size() > 0);
         assertTrue("recommendation result id exists", response.getResultId() != null);
     }
 
+    @Test
+    public void getRecommendationsShouldErrorWithVariationIdAndNoItemIds() throws Exception {
+        ConstructorIO constructor = new ConstructorIO("", apiKey, true, null);
+        UserInfo userInfo = new UserInfo(3, "c62a-2a09-faie");
+        RecommendationsRequest request = new RecommendationsRequest("item_page_1");
+        request.setVariationId("power_drill_variation");
+
+        thrown.expect(ConstructorException.class);
+        thrown.expectMessage("variationId requires exactly one itemId to be specified");
+        constructor.recommendations(request, userInfo);
+    }
+
+    @Test
+    public void getRecommendationsShouldErrorWithVariationIdAndMultipleItemIds() throws Exception {
+        ConstructorIO constructor = new ConstructorIO("", apiKey, true, null);
+        UserInfo userInfo = new UserInfo(3, "c62a-2a09-faie");
+        RecommendationsRequest request = new RecommendationsRequest("item_page_1");
+        request.setItemIds(Arrays.asList("power_drill", "drill"));
+        request.setVariationId("power_drill_variation");
+
+        thrown.expect(ConstructorException.class);
+        thrown.expectMessage("variationId requires exactly one itemId to be specified");
+        constructor.recommendations(request, userInfo);
+    }
+
     @Test
     public void getRecommendationsShouldReturnAResultWithMultipleItemIds() throws Exception {
         ConstructorIO constructor = new ConstructorIO("", apiKey, true, null);