diff --git a/deno.json b/deno.json
new file mode 100644
index 0000000..2303ea3
--- /dev/null
+++ b/deno.json
@@ -0,0 +1,7 @@
+{
+    "tasks":
+    {
+        "fs": "deno run -A https://deno.land/std@0.166.0/http/file_server.ts",
+        "test": "deno test *_test.js --watch"
+    }
+}
\ No newline at end of file
diff --git a/deno.lock b/deno.lock
new file mode 100644
index 0000000..0ecd71f
--- /dev/null
+++ b/deno.lock
@@ -0,0 +1,9 @@
+{
+  "version": "2",
+  "remote": {
+    "https://deno.land/std@0.166.0/fmt/colors.ts": "9e36a716611dcd2e4865adea9c4bec916b5c60caad4cdcdc630d4974e6bb8bd4",
+    "https://deno.land/std@0.166.0/testing/_diff.ts": "a23e7fc2b4d8daa3e158fa06856bedf5334ce2a2831e8bf9e509717f455adb2c",
+    "https://deno.land/std@0.166.0/testing/_format.ts": "cd11136e1797791045e639e9f0f4640d5b4166148796cad37e6ef75f7d7f3832",
+    "https://deno.land/std@0.166.0/testing/asserts.ts": "1e340c589853e82e0807629ba31a43c84ebdcdeca910c4a9705715dfdb0f5ce8"
+  }
+}
diff --git a/store.js b/store.js
index a5d368e..e9b45db 100644
--- a/store.js
+++ b/store.js
@@ -58,52 +58,61 @@ export const Initial =
 /** @typedef {{Name:"Test", Data:number}} ActionTest*/
 /** @typedef {ActionMark|ActionTest} Action */
 /** @typedef {(inState:State, inAction:Action)=>State} Reducer */
+/** @typedef {(inState:State)=>boolean} SelectionUpdater */
+/** @type {Record<string, SelectionUpdater>} */
+const Update = {
+    Freq(inState)
+    {
+        const column = ColumnMapping[inState.Freq];
+        if(column && inState.Selection.Test)
+        {
+            const hz = column[0];
+            inState.Selection.Freq = undefined;
+            for(let i=0; i<inState.Selection.Test.Plot.length; i++)
+            {
+                const plot = inState.Selection.Test.Plot[i];
+                if(plot.Hz == hz)
+                {
+                    inState.Selection.Freq = plot;
+                    return true;
+                }
+            }
+        }
+        return false;
+    },
+    Mark(inState)
+    {
+        const freq = inState.Selection.Freq;
+        if(freq)
+        {
+            if(inState.Chan == "left" && freq.UserL)
+            {
+                inState.Selection.Mark = freq.UserL;
+                return true;
+            }
+            else if(inState.Chan == "right" && freq.UserR)
+            {
+                inState.Selection.Mark = freq.UserR;
+                return true;
+            }
+        }
+        return false;
+    }
+};
 /** @type {Reducer} */
 export function Reducer(inState, inAction)
 {
     const clone = {...inState};
+
     switch(inAction.Name)
     {
         case "Test" :
         {
-
-            let selTest = clone.Tests[inAction.Data];
-            let selFreq = undefined;
-            let selMark = undefined;
-            const column = ColumnLookup(clone.Freq);
-            if(column)
-            {
-                let hz = column[0];
-                let plot;
-                for(let i=0; i<selTest.Plot.length; i++)
-                {
-                    plot = selTest.Plot[i];
-                    if(plot.Hz == hz)
-                    {
-                        selFreq = plot;
-                        if(clone.Chan == "left" && selFreq.UserL)
-                        {
-                            selMark = selFreq.UserL;
-                        }
-                        else if(clone.Chan == "right" && selFreq.UserR)
-                        {
-                            selMark = selFreq.UserR;
-                        }
-                    }
-                }
-            }
-            const freq = test.Plot[]
-            //clone.Selection = {...clone.Selection, Test:clone.Tests[inAction.Data]}
+            clone.Selection.Test = clone.Tests[inAction.Data];
+            Update.Freq(clone);
+            Update.Mark(clone);
             break;
         }
-        case "Mark" :
-        {
-            if(clone.Test)
-            {
-                clone.Test.Plot
-
-            }
-        }
     }
     return clone;
 }
\ No newline at end of file
diff --git a/store_test.js b/store_test.js
new file mode 100644
index 0000000..1be2737
--- /dev/null
+++ b/store_test.js
@@ -0,0 +1,61 @@
+import { assertEquals } from "https://deno.land/std@0.166.0/testing/asserts.ts";
+import { Initial, Reducer, ColumnMapping } from "./store.js";
+
+const States = {
+    list:[],
+    get latest()
+    {
+        return this.list[this.list.length-1];
+    },
+    set latest(input)
+    {
+        this.list.push(input);
+    }
+};
+
+States.latest = Initial;
+
+Deno.test("Initial State", async (t)=>
+{
+    const state = Initial;
+
+    await t.step("Selections are empty", ()=>
+    {
+        assertEquals(state.Selection.Test, undefined);
+        assertEquals(state.Selection.Freq, undefined);
+        assertEquals(state.Selection.Mark, undefined);
+    });
+
+    await t.step("Frequency index maps to 1k hz", ()=>
+    {
+        assertEquals(state.Freq, 3);
+        assertEquals(ColumnMapping[state.Freq][0], 1000);
+    });
+
+    await t.step("The first test has its 2nd plot at 1k hz, and no user marks", ()=>
+    {
+        const plot = state.Tests[0].Plot[1];
+        assertEquals(plot.Hz, 1000);
+        assertEquals(plot.UserL, undefined);
+        assertEquals(plot.UserR, undefined);
+    });
+})
+
+Deno.test("Select Test", async (t)=>
+{
+    let state;
+    await t.step("dispatch action", ()=>
+    {
+        state = Reducer(Initial, {Name:"Test", Data:0});
+    });
+    
+    await t.step("check selections: test and freq, but no mark", ()=>
+    {
+        assertEquals(state.Selection.Test, state.Tests[0]);
+        assertEquals(state.Selection.Freq, state.Tests[0].Plot[1]);
+        assertEquals(state.Selection.Mark, undefined);
+    });
+
+
+    
+})