Add tests and fix for usage of count with grouping (#13531)

* fix(model): convert count to number when grouping

* test(model#count): fix ordering issue in count test

lib/model.js

@@ -2034,7 +2034,18 @@ class Model {
     options.offset = null;
     options.order = null;
 
-    return await this.aggregate(col, 'count', options);
+    const result = await this.aggregate(col, 'count', options);
+
+    // When grouping is used, some dialects such as PG are returning the count as string
+    // --> Manually convert it to number
+    if (Array.isArray(result)) {
+      return result.map(item => ({
+        ...item,
+        count: Number(item.count)
+      }));
+    }
+
+    return result;
   }
 
   /**

test/integration/associations/has-many.test.js

@@ -1352,6 +1352,7 @@ describe(Support.getTestDialectTeaser('HasMany'), () => {
       });
 
       expect(count.length).to.equal(1);
+      expect(count).to.deep.equal([{ userId: 1, count: 1 }]);
       expect(rows[0].tasks[0].jobs.length).to.equal(2);
     });
   });

test/integration/model.test.js

@@ -1720,6 +1720,10 @@ describe(Support.getTestDialectTeaser('Model'), () => {
         group: ['data']
       });
       expect(count).to.have.lengthOf(2);
+
+      // The order of count varies across dialects; Hence find element by identified first.
+      expect(count.find(i => i.data === 'A')).to.deep.equal({ data: 'A', count: 2 });
+      expect(count.find(i => i.data === 'B')).to.deep.equal({ data: 'B', count: 1 });
     });
 
     if (dialect !== 'mssql') {