src/gm_ctflow.erl

@@ -1,5 +1,30 @@
 -module(gm_ctflow).
 
--type flow() :: any().
+-export([ put/2
+        , get/1
+        , get/2
+        , erase/1
+        ]).
+
+-type flow()  :: any().
+-type key()   :: any().
+-type value() :: any().
 
 -export_type([ flow/0 ]).
+
+-spec put(key(), value()) -> 'ok'.
+put(Key, Value) ->
+    gm_ctflow_state:put(Key, Value).
+
+-spec get(key()) -> value() | no_return().
+get(Key) ->
+    gm_ctflow_state:get(Key).
+
+-spec get(key(), Default) -> value()
+                 when Default :: value().
+get(Key, Default) ->
+    gm_ctflow_state:get(Key, Default).
+
+-spec erase(key()) -> 'ok'.
+erase(Key) ->
+    gm_ctflow_state:erase(Key).

src/gm_ctflow_app.erl

@@ -10,6 +10,7 @@
 -export([start/2, stop/1]).
 
 start(_StartType, _StartArgs) ->
+    gm_ctflow_state:init(),
     gm_ctflow_sup:start_link().
 
 stop(_State) ->

src/gm_ctflow_state.erl

@@ -0,0 +1,42 @@
+-module(gm_ctflow_state).
+
+-export([ init/0
+        , put/2
+        , get/1
+        , get/2
+        , erase/1 ]).
+
+-type key()   :: any().
+-type value() :: any().
+
+
+init() ->
+    ets:new(?MODULE, [ordered_set, public, named_table]).
+
+-spec put(key(), value()) -> 'ok'.
+put(Key, Value) ->
+    ets:insert(?MODULE, {Key, Value}),
+    ok.
+
+-spec get(key()) -> value() | no_return().
+get(Key) ->
+    case ets:lookup(?MODULE, Key) of
+        [] ->
+            error({no_such_key, Key});
+        [{_, Value}] ->
+            Value
+    end.
+
+-spec get(key(), Default) -> value()
+              when Default :: value().
+get(Key, Default) ->
+    case ets:lookup(?MODULE, Key) of
+        [{_, Value}] ->
+            Value;
+        [] ->
+            Default
+    end.
+
+erase(Key) ->
+    ets:delete(?MODULE, Key),
+    ok.

test/gm_ctflow_SUITE.erl

@@ -11,7 +11,10 @@
         ]).
 
 %% test cases
--export([ init_counter/1
+-export([ put_a/1
+        , get_a/1
+        , erase_a/1
+        , init_counter/1
         , incr/1
         , check1/1
         , check2/1
@@ -27,12 +30,17 @@
 
 all() ->
     [
-      {group, statefuns}
+      {group, state}
+    , {group, statefuns}
     , {group, workers}
     ].
 
 groups() ->
-    [ {statefuns, [sequence], [ init_counter
+    [ {state, [sequence], [ put_a
+                          , get_a
+                          , erase_a
+                          ]}
+    , {statefuns, [sequence], [ init_counter
                               , incr
                               , check1       %% state = 1
                               , incr
@@ -71,6 +79,21 @@ init_per_testcase(_Case, Config) ->
 end_per_testcase(_Case, _Config) ->
     ok.
 
+%% ======================================================================
+%% State update commands
+
+put_a(_Cfg) ->
+    ok = gm_ctflow:put(a, 1),
+    ?assertMatch(1, gm_ctflow:get(a)).
+
+get_a(_Cfg) ->
+    ?assertMatch(1, gm_ctflow:get(a)).
+
+erase_a(_Cfg) ->
+    ok = gm_ctflow:erase(a),
+    ?assertException(error, {no_such_key,a}, gm_ctflow:get(a)),
+    ?assertMatch(undefined, gm_ctflow:get(a, undefined)).
+
 %% ======================================================================
 %% This is our 'ctflow_fun' instance, which floats above some simple
 %% test cases. In this test suite, we only exercise the flow funs, but