diff --git a/test/monger/test/atomic_modifiers.clj b/test/monger/test/atomic_modifiers.clj
new file mode 100644
index 0000000..8e57d7f
--- /dev/null
+++ b/test/monger/test/atomic_modifiers.clj
@@ -0,0 +1,50 @@
+(set! *warn-on-reflection* true)
+
+(ns monger.test.atomic-modifiers
+  (:import  [com.mongodb WriteResult WriteConcern DBCursor DBObject CommandResult$CommandFailure]
+            [org.bson.types ObjectId])
+  (:require [monger core util]
+            [monger.collection :as mgcol]
+            [monger.result     :as mgres])
+  (:use [clojure.test]
+        [monger.test.fixtures]))
+
+
+(use-fixtures :each purge-docs-collection purge-things-collection)
+
+(monger.core/set-default-write-concern! WriteConcern/SAFE)
+
+
+
+;;
+;; $set
+;;
+
+(deftest update-a-single-existing-field-using-$set-operator
+  (let [coll "things"
+        oid  (ObjectId.)]
+    (mgcol/insert coll { :_id oid :weight 10.0 })
+    (mgcol/update coll { :_id oid } { "$set" { :weight 20.5 } })
+    (is (= 20.5 (:weight (mgcol/find-map-by-id coll oid [:weight]))))))
+
+(deftest set-a-single-non-existing-field-using-$set-operator
+  (let [coll "things"
+        oid  (ObjectId.)]
+    (mgcol/insert coll { :_id oid :weight 10.0 })
+    (mgcol/update coll { :_id oid } { "$set" { :height 17.2 } })
+    (is (= 17.2 (:height (mgcol/find-map-by-id coll oid [:height]))))))
+
+(deftest update-multiple-existing-fields-using-$set-operator
+  (let [coll "things"
+        oid  (ObjectId.)]
+    (mgcol/insert coll { :_id oid :weight 10.0 :height 15.2 })
+    (mgcol/update coll { :_id oid } { "$set" { :weight 20.5 :height 25.6 } })
+    (is (= { :_id oid :weight 20.5 :height 25.6 } (mgcol/find-map-by-id coll oid [:weight])))))
+
+
+(deftest update-and-set-multiple-fields-using-$set-operator
+  (let [coll "things"
+        oid  (ObjectId.)]
+    (mgcol/insert coll { :_id oid :weight 10.0 })
+    (mgcol/update coll { :_id oid } { "$set" { :weight 20.5 :height 25.6 } })
+    (is (= { :_id oid :weight 20.5 :height 25.6 } (mgcol/find-map-by-id coll oid [:weight])))))
diff --git a/test/monger/test/collection.clj b/test/monger/test/collection.clj
index 8d28fa2..94a1a67 100644
--- a/test/monger/test/collection.clj
+++ b/test/monger/test/collection.clj
@@ -10,37 +10,13 @@
             [monger.result     :as mgres]
             [monger.conversion :as mgcnv]
             [monger.js         :as js])
-  (:use [clojure.test]))
+  (:use [clojure.test]
+        [monger.test.fixtures]))
 
 (monger.core/connect!)
 (monger.core/set-db! (monger.core/get-db "monger-test"))
 
 
-;;
-;; fixture functions
-;;
-
-(defn purge-collection
-  [collection-name, f]
-  (mgcol/remove collection-name)
-  (f)
-  (mgcol/remove collection-name))
-
-(defn purge-people-collection
-  [f]
-  (purge-collection "people" f))
-
-(defn purge-docs-collection
-  [f]
-  (purge-collection "docs" f))
-
-(defn purge-things-collection
-  [f]
-  (purge-collection "things" f))
-
-(defn purge-libraries-collection
-  [f]
-  (purge-collection "libraries" f))
 
 (use-fixtures :each purge-people-collection purge-docs-collection purge-things-collection purge-libraries-collection)
 
diff --git a/test/monger/test/fixtures.clj b/test/monger/test/fixtures.clj
new file mode 100644
index 0000000..de6e721
--- /dev/null
+++ b/test/monger/test/fixtures.clj
@@ -0,0 +1,28 @@
+(ns monger.test.fixtures
+  (:require [monger.collection :as mgcol]))
+
+;;
+;; fixture functions
+;;
+
+(defn purge-collection
+  [collection-name, f]
+  (mgcol/remove collection-name)
+  (f)
+  (mgcol/remove collection-name))
+
+(defn purge-people-collection
+  [f]
+  (purge-collection "people" f))
+
+(defn purge-docs-collection
+  [f]
+  (purge-collection "docs" f))
+
+(defn purge-things-collection
+  [f]
+  (purge-collection "things" f))
+
+(defn purge-libraries-collection
+  [f]
+  (purge-collection "libraries" f))