diff --git a/src/mount/core.cljc b/src/mount/core.cljc
index ea125cc..95549dd 100644
--- a/src/mount/core.cljc
+++ b/src/mount/core.cljc
@@ -1,6 +1,7 @@
 (ns mount.core
   #?(:clj (:require [mount.tools.macro :refer [on-error throw-runtime] :as macro]
                     [mount.tools.logger :refer [log]]
+                    [clojure.set :refer [intersection]]
                     [clojure.string :as s])
      :cljs (:require [mount.tools.macro :as macro]
                      [mount.tools.logger :refer [log]]))
@@ -250,11 +251,16 @@
 
 ;; composable set of states
 
+(defn- mapset [f xs]
+  (-> (map f xs)
+      set))
+
 (defn only
   ([states]
-   states)
+   (only (find-all-states) states))
   ([states these]
-   (filter these states)))
+   (intersection (mapset var-to-str these)
+                 (mapset var-to-str states))))
 
 (defn with-args 
   ([args]
@@ -267,7 +273,8 @@
   ([states]
    (except (find-all-states) states))
   ([states these]
-   (remove these states)))
+   (remove (mapset var-to-str these)
+           (mapset var-to-str states))))
 
 (defn swap
   ([with]
@@ -287,13 +294,6 @@
                   (var-to-str to) :state))
    states))
 
-#_(-> (only #{1 2 3 4})
-      (with-args {})
-      (except #{2 1})
-      (swap {2 42 1 34})
-      (swap-states {4 "#'foo.bar/42"})
-      (start))
-
 ;; explicit, not composable (subject to depreciate?)
 
 (defn stop-except [& states]
diff --git a/test/core/mount/test/composable_fns.cljc b/test/core/mount/test/composable_fns.cljc
new file mode 100644
index 0000000..43703a0
--- /dev/null
+++ b/test/core/mount/test/composable_fns.cljc
@@ -0,0 +1,90 @@
+(ns mount.test.composable-fns
+  (:require
+    #?@(:cljs [[cljs.test :as t :refer-macros [is are deftest testing use-fixtures]]
+               [clojure.set :refer [intersection]]
+               [mount.core :refer [only except swap swap-states with-args] :as mount :refer-macros [defstate]]
+               [tapp.websockets :refer [system-a]]
+               [tapp.conf :refer [config]]
+               [tapp.audit-log :refer [log]]]
+        :clj  [[clojure.test :as t :refer [is are deftest testing use-fixtures]]
+               [clojure.set :refer [intersection]]
+               [mount.core :as mount :refer [defstate only except swap swap-states with-args]]
+               [tapp.conf :refer [config]]
+               [tapp.nyse :refer [conn]]
+               [tapp.example :refer [nrepl]]])
+   [mount.test.helper :refer [dval helper]]))
+
+#?(:clj (alter-meta! *ns* assoc ::load false))
+
+(defstate test-conn :start 42
+                    :stop (constantly 0))
+
+(defstate test-nrepl :start [])
+
+#?(:clj
+  (deftest only-states
+
+    (testing "only should only return given states. 
+              if source set of states is not provided, it should use all the states to select from"
+      (is (= #{"#'mount.test.composable-fns/test-conn" "#'tapp.example/nrepl" "#'tapp.nyse/conn"} 
+             (only #{"#'is.not/here" #'mount.test.composable-fns/test-conn #'tapp.example/nrepl #'tapp.nyse/conn}))))
+
+    (testing "only should only return given states"
+      (is (= #{"#'mount.test.composable-fns/test-conn" "#'tapp.example/nrepl"} 
+             (only [#'mount.test.composable-fns/test-conn #'tapp.example/nrepl #'tapp.nyse/conn] 
+                   #{"#'is.not/here" #'mount.test.composable-fns/test-conn #'tapp.example/nrepl}))))))
+
+#?(:clj
+  (deftest except-states
+
+    (testing "except should exclude given states.
+              if source set of states is not provided, it should use all the states to exclude from"
+      (let [states (except #{"#'is.not/here" #'tapp.example/nrepl #'tapp.nyse/conn})]
+        (is (coll? states))
+        (is (pos? (count states)))
+        (is (zero? (count (intersection (set states)
+                                        #{"#'tapp.example/nrepl" "#'tapp.nyse/conn" "#'is.not/here"}))))))
+
+    (testing "except should exclude given states"
+      (is (= #{"#'tapp.conf/config" "#'mount.test.composable-fns/test-conn"}
+             (set (except #{#'tapp.example/nrepl #'tapp.conf/config #'mount.test.composable-fns/test-conn}
+                          #{"#'is.not/here" #'tapp.example/nrepl #'tapp.nyse/conn})))))))
+
+#?(:clj
+  (deftest states-with-args
+
+    (testing "with-args should set args and return all states if none provided"
+      (let [states (with-args {:a 42})]
+        (is (= {:a 42} (mount/args)))
+        (is (= states (#'mount.core/find-all-states)))))
+
+    (testing "with-args should set args and thread states if provided"
+      (let [t-states #{"#'is.not/here" #'mount.test.composable-fns/test-conn #'tapp.example/nrepl #'tapp.nyse/conn}
+            states (with-args t-states {:a 42})]
+        (is (= {:a 42} (mount/args)))
+        (is (= states t-states))))))
+
+#?(:clj
+  (deftest swap-states-with-values
+
+    (testing "swap should swap states with values and return all states if none is given"
+      (let [states (swap {#'tapp.nyse/conn "conn-sub"
+                          #'tapp.example/nrepl :nrepl-sub})]
+        (is (= states (#'mount.core/find-all-states)))
+        (mount/start)
+        (is (map? (dval config)))
+        (is (= :nrepl-sub (dval nrepl)))
+        (is (= "conn-sub" (dval conn)))
+        (mount/stop)))
+
+    (testing "swap should swap states with values and return only states that it is given"
+      (let [t-states #{"#'is.not/here" #'mount.test.composable-fns/test-conn #'tapp.example/nrepl #'tapp.nyse/conn}
+            states (swap t-states {#'tapp.nyse/conn "conn-sub"
+                                   #'tapp.example/nrepl :nrepl-sub})]
+        (is (= states t-states))
+        (mount/start)
+        (is (map? (dval config)))
+        (is (= :nrepl-sub (dval nrepl)))
+        (is (= "conn-sub" (dval conn)))
+        (is (= 42 (dval test-conn)))
+        (mount/stop)))))