2 files changed, 165 insertions, 0 deletions
diff --git a/jstests/aggregation/sources/addFields/use_cases.js b/jstests/aggregation/sources/addFields/use_cases.js
new file mode 100644
index 00000000000..725408fb40d
--- /dev/null
+++ b/jstests/aggregation/sources/addFields/use_cases.js
@@ -0,0 +1,64 @@
+/**
+ * $addFields can be used to add fixed and computed fields to documents while preserving the
+ * original document. Verify that using $addFields and adding computed fields in a $project yield
+ * the same result.
+ */
+
+(function() {
+    "use strict";
+
+    // For arrayEq.
+    load("jstests/aggregation/extras/utils.js");
+
+    const dbName = "test";
+    const collName = jsTest.name();
+
+    function doExecutionTest(conn) {
+        const coll = conn.getDB(dbName).getCollection(collName);
+        coll.drop();
+
+        // Insert a bunch of documents of the form above.
+        const nDocs = 10;
+        for (let i = 0; i < nDocs; i++) {
+            assert.writeOK(coll.insert({"_id": i, "2i": i * 2, "3i": i * 3}));
+        }
+
+        // Add the minimum, maximum, and average temperatures, and make sure that doing the same
+        // with addFields yields the correct answer.
+        // First compute with $project, since we know all the fields in this document.
+        let projectPipe = [{
+            $project: {
+                "2i": 1,
+                "3i": 1,
+                "6i^2": {"$multiply": ["$2i", "$3i"]},
+                // _id is implicitly included.
+            }
+        }];
+        let correct = coll.aggregate(projectPipe).toArray();
+
+        // Then compute the same results using $addFields.
+        let addFieldsPipe = [{
+            $addFields: {
+                "6i^2": {"$multiply": ["$2i", "$3i"]},
+                // All other fields are implicitly included.
+            }
+        }];
+        let addFieldsResult = coll.aggregate(addFieldsPipe).toArray();
+
+        // Then assert they are the same.
+        assert(arrayEq(addFieldsResult, correct),
+               "$addFields does not work the same as a $project with computed and included fields");
+    }
+
+    // Test against the standalone started by resmoke.py.
+    let conn = db.getMongo();
+    doExecutionTest(conn);
+    print("Success! Standalone execution use case test for $addFields passed.");
+
+    // Test against a sharded cluster.
+    let st = new ShardingTest({shards: 2});
+    doExecutionTest(st.s0);
+    st.stop();
+    print("Success! Sharding use case test for $addFields passed.");
+
+}());
+\ No newline at end of file
diff --git a/jstests/aggregation/sources/addFields/weather.js b/jstests/aggregation/sources/addFields/weather.js
new file mode 100644
index 00000000000..7e2be837329
--- /dev/null
+++ b/jstests/aggregation/sources/addFields/weather.js
@@ -0,0 +1,101 @@
+/**
+ * $addFields can be used to add fixed and computed fields to documents while preserving the
+ * original document. Verify that using $addFields and adding computed fields in a $project yield
+ * the same result. Use the sample case of computing weather metadata.
+ */
+
+(function() {
+    "use strict";
+
+    // For arrayEq.
+    load("jstests/aggregation/extras/utils.js");
+
+    const dbName = "test";
+    const collName = jsTest.name();
+
+    Random.setRandomSeed();
+
+    /**
+     * Helper to generate an array of specified length of numbers in the specified range.
+     */
+    function randomArray(length, minValue, maxValue) {
+        let array = [];
+        for (let i = 0; i < length; i++) {
+            array.push((Random.rand() * (maxValue - minValue)) + minValue);
+        }
+        return array;
+    }
+
+    /**
+     * Helper to generate a randomized document with the following schema:
+     * {
+     *    month: <integer month of year>,
+     *    day: <integer day of month>,
+     *    temperatures: <array of 24 decimal temperatures>
+     * }
+     */
+    function generateRandomDocument() {
+        const minTemp = -40;
+        const maxTemp = 120;
+
+        return {
+            month: Random.randInt(12) + 1,  // 1-12
+            day: Random.randInt(31) + 1,    // 1-31
+            temperatures: randomArray(24, minTemp, maxTemp),
+        };
+    }
+
+    function doExecutionTest(conn) {
+        const coll = conn.getDB(dbName).getCollection(collName);
+        coll.drop();
+
+        // Insert a bunch of documents of the form above.
+        const nDocs = 10;
+        for (let i = 0; i < nDocs; i++) {
+            assert.writeOK(coll.insert(generateRandomDocument()));
+        }
+
+        // Add the minimum, maximum, and average temperatures, and make sure that doing the same
+        // with addFields yields the correct answer.
+        // First compute with $project, since we know all the fields in this document.
+        let projectWeatherPipe = [{
+            $project: {
+                "month": 1,
+                "day": 1,
+                "temperatures": 1,
+                "minTemp": {"$min": "$temperatures"},
+                "maxTemp": {"$max": "$temperatures"},
+                "average": {"$avg": "$temperatures"},
+                // _id is implicitly included.
+            }
+        }];
+        let correctWeather = coll.aggregate(projectWeatherPipe).toArray();
+
+        // Then compute the same results using $addFields.
+        let addFieldsWeatherPipe = [{
+            $addFields: {
+                "minTemp": {"$min": "$temperatures"},
+                "maxTemp": {"$max": "$temperatures"},
+                "average": {"$avg": "$temperatures"},
+                // All other fields are implicitly included.
+            }
+        }];
+        let addFieldsResult = coll.aggregate(addFieldsWeatherPipe).toArray();
+
+        // Then assert they are the same.
+        assert(arrayEq(addFieldsResult, correctWeather),
+               "$addFields does not work the same as a $project with computed and included fields");
+    }
+
+    // Test against the standalone started by resmoke.py.
+    let conn = db.getMongo();
+    doExecutionTest(conn);
+    print("Success! Standalone execution weather test for $addFields passed.");
+
+    // Test against a sharded cluster.
+    let st = new ShardingTest({shards: 2});
+    doExecutionTest(st.s0);
+    st.stop();
+    print("Success! Sharding weather test for $addFields passed.");
+
+}());
+\ No newline at end of file