diff --git a/static/lib.mjs b/static/lib.mjs
index d16ea49..af96fdf 100644
--- a/static/lib.mjs
+++ b/static/lib.mjs
@@ -271,6 +271,10 @@ export class GraphPlot extends HTMLElement {
         return name;
     }
 
+    getFilterLabels() {
+        return this.#filterLabels;
+    }
+
     /**
      * @param {Object<string, string>} labels
      */
diff --git a/tests/TAP.mjs b/tests/TAP.mjs
new file mode 100644
index 0000000..db29659
--- /dev/null
+++ b/tests/TAP.mjs
@@ -0,0 +1,454 @@
+/**
+* Tap - a 0 dependency TAP compliant test library useable from the commandline
+* 
+* ```js
+* import { Tap } from './src/TAP.mjs';
+* var t = new Tap;
+* t.plan(3);
+* 
+* t.ok(true, 'True is True'); # test will pass
+* t.is(1, 2, 'one is two'); # test will fail
+* 
+* var obj = {};
+* obj.method1 = function() { return true; };
+* 
+* t.can_ok(obj, 'method1'); # test will pass
+* ```
+* 
+* @module TAP
+* @license Artistic-2.0
+*/
+
+/** @implements TapRenderer */
+class NodeRenderer {
+    /** @type {Array<PromiseLike>} */
+    #thunks = [];
+
+    out(text) {
+        this.#thunks.push(
+            // Because this is a ECMAScript module we have to do dynamic module loads
+            // of the node ecosystem when running in Node.js.
+            import('node:process').then(loaded => {
+                loaded.stdout.write(text + "\n");
+        }));
+    }
+
+    comment(lines) {
+        for (var line of lines) {
+            this.out('# ' + line);
+        }
+    }
+
+    // This gives us a way to block on output. It's ghetto but async is a harsh task master.
+    async renderAll() {
+        for (var thunk of this.#thunks) {
+            await thunk;
+        }
+
+    }
+}
+
+/** @implements TapRenderer */
+class BrowserRenderer {
+    #target = document.body;
+
+    /** @param {HtmlElement=} target */
+    constructor(target) {
+        if (target) {
+            this.#target = target;
+        }
+    }
+
+    /** @returns TextNode */
+    #createText(text) {
+        return document.createTextNode(text);
+    }
+
+    /**
+     * @param {Node} nodes 
+     * @returns HTMLDivElement
+     */
+    #createDiv(nodes) {
+        const div = document.createElement("div");
+        div.append(...nodes);
+        return div;
+    }
+
+    out(text) {
+        const textNode = this.#createText(text);
+        var div = this.#createDiv([textNode]);
+        if (text.startsWith("not ok")) {
+            div.setAttribute("class", "fail");
+        } else if (text.startsWith("ok")) {
+            div.setAttribute("class", "pass");
+        }
+        this.#target.appendChild(div);
+    }
+
+    comment(lines) {
+        // TODO(jeremy):
+        var elems = [];
+        for (var line of lines) {
+            elems.push(this.#createText("# " + line), document.createElement("br"));
+        }
+        var commentDiv = this.#createDiv(elems);
+        commentDiv.setAttribute("class", "comment");
+        this.#target.appendChild(commentDiv);
+    }
+}
+
+/**
+ * The Tap Test Class helper.
+ */
+class Tap {
+    /** @type Number? */
+    planned = null;
+    /** @type Number */
+    counter = 0;
+    /** @type Number */
+    passed = 0;
+    /** @type Number */
+    failed = 0;
+    /** @type TapRenderer */
+    renderer
+
+    /**
+     * Construct a new Tap Suite with a renderLine function.
+     * @param {TapRenderer}
+     */
+    constructor(renderer) {
+        this.renderer = renderer;
+    }
+
+    /**
+     * @return {{"Renderer": BrowserRenderer, "Tap": Tap}}
+     */
+    static Browser() {
+        var r = new BrowserRenderer();
+        return {"Renderer": r, "Tap": new Tap(r)};
+        return new Tap(new BrowserRenderer());
+    }
+
+    /**
+     * @return {{"Renderer": NodeRenderer, "Tap": Tap}}
+     */
+    static Node() {
+        var r = new NodeRenderer();
+        return {"Renderer": r, "Tap": new Tap(r)};
+    }
+
+    isPass() {
+        return this.passed != 0;
+    }
+
+    /** Renders output for the test results */
+    out(text) {
+        this.renderer.out(text);
+    };
+
+    /**
+     * Construct a Tap output message.
+     *
+     * @param {boolean} ok
+     * @param {string=} description 
+     */
+    mk_tap(ok, description) {
+        if (!this.planned) {
+            this.out("You tried to run tests without a plan.  Gotta have a plan.");
+            throw new Error("You tried to run tests without a plan.  Gotta have a plan.");
+        }
+        this.counter++;
+        this.out(ok + ' ' + this.counter + ' - ' + (description || ""));
+    };
+
+
+    comment(msg) {
+        if (!msg) {
+            msg = " ";
+        }
+        var lines = msg.split("\n");
+        this.renderer.comment(lines);
+    };
+
+    /** Render a pass TAP output message.
+     * @param {string} description 
+     */
+    pass(description) {
+        this.passed++;
+        this.mk_tap('ok', description);
+    };
+
+    /** Render a fail TAP output message.
+     * @param {string} description 
+     */
+    fail(description) {
+        this.failed++;
+        this.mk_tap('not ok', description);
+    };
+
+    /** Run a function as a TODO test.
+     *
+     * @param {function(this:Tap, boolean, description)} func 
+     */
+    todo(func) {
+        var self = this;
+        var tapper = self.mk_tap;
+        self.mk_tap = function(ok, desc) {
+            tapper.apply(self, [ok, "# TODO: " + desc]);
+        }
+        func();
+        self.mk_tap = tapper;
+    }
+
+    /** Run a function as a skip Test.
+     *
+     * @param {boolean} criteria 
+     * @param {string} reason 
+     * @param {number} count - The number of tests to skip 
+     * @param {function(this:Tap, boolean, description)} func 
+     */
+    skip(criteria, reason, count, func) {
+        var self = this;
+        if (criteria) {
+            var tapper = self.mk_tap;
+            self.mk_tap = function(ok, desc) {
+                tapper.apply(self, [ok, desc]);
+            }
+            for (var i = 0; i < count; i++) {
+                self.fail("# SKIP " + reason)
+            }
+            self.mk_tap = tapper;
+        } else {
+            func();
+        }
+    }
+
+    /** Sets the test plan.
+     * Once set this can not be reset again. Any attempt to change the plan once already
+     * set will throw an exception.
+     *
+     * Call with no arguments if you don't want to specify the number of tests to run.
+     *
+     * @param {Number=} testCount 
+     */
+    plan(testCount) {
+        if (this.planned) {
+            throw new Error("you tried to set the plan twice!");
+        }
+        if (!testCount) {
+            this.planned = 'no_plan';
+        } else {
+            this.planned = testCount;
+            this.out('1..' + testCount);
+        }
+    };
+
+    #pass_if(func, desc) {
+        var result = func();
+        if (result) { this.pass(desc) }
+        else { this.fail(desc) }
+    }
+
+    // exception tests
+
+    /**
+     * Tests that a function throws with a given error message.
+     *
+     * @param {function()} func
+     * @param {RegExp} msg 
+     */
+    throws_ok(func, msg) {
+        var errormsg = ' ';
+        if (typeof func != 'function')
+            this.comment('throws_ok needs a function to run');
+
+        try {
+            func();
+        }
+        catch (err) {
+            errormsg = err + '';
+        }
+        this.like(errormsg, msg, 'code threw [' + errormsg + '] expected: [' + msg + ']');
+    }
+
+    /**
+     * Tests that a function throws.
+     *
+     * @param {function()} func
+     */
+    dies_ok(func) {
+        var errormsg = ' ';
+        var msg = false;
+        if (typeof func != 'function')
+            this.comment('throws_ok needs a function to run');
+
+        try {
+            func();
+        }
+        catch (err) {
+            errormsg = err + '';
+            msg = true;
+        }
+        this.ok(msg, 'code died with [' + errormsg + ']');
+    }
+
+    /**
+     * Tests that a function does not throw an exception.
+     *
+     * @param {function()} func
+     */
+    lives_ok(func, msg) {
+        var errormsg = true;
+        if (typeof func != 'function')
+            this.comment('throws_ok needs a function to run');
+
+        try {
+            func();
+        }
+        catch (err) {
+            errormsg = false;
+        }
+        this.ok(errormsg, msg);
+    }
+
+    /**
+     * Tests that an object has a given method or function.
+     *
+     * @param {*} obj 
+     */
+    can_ok(obj) {
+        var desc = 'object can [';
+        var pass = true;
+        for (var i = 1; i < arguments.length; i++) {
+            if (typeof (obj[arguments[i]]) != 'function') {
+                if (typeof (obj.prototype) != 'undefined') {
+                    var result = typeof eval('obj.prototype.' + arguments[i]);
+                    if (result == 'undefined') {
+                        pass = false;
+                        this.comment('Missing ' + arguments[i] + ' method');
+                    }
+                } else {
+                    pass = false;
+                    this.comment('Missing ' + arguments[i] + ' method');
+                }
+            }
+            desc += ' ' + arguments[i];
+        }
+        desc += ' ]';
+        this.#pass_if(function() {
+            return pass;
+        }, desc);
+
+    }
+
+    /**
+     * Tests that two given objects are equal.
+     *
+     * @param {*} got 
+     * @param {*} expected
+     * @param {string} desc 
+     */
+    is(got, expected, desc) {
+        this.#pass_if(function() { return got == expected; }, desc);
+    };
+
+
+    /**
+     * Test that expression evaluates to true value
+     *
+     * @param {*} got
+     * @param {string} desc 
+     */
+    ok(got, desc) {
+        this.#pass_if(function() { return !!got; }, desc);
+    };
+
+
+    /**
+     * Tests that a string matches the regex.
+     *
+     * @param {string} string
+     * @param {RegExp} regex
+     * @param {string} desc 
+     */
+    like(string, regex, desc) {
+        this.#pass_if(function() {
+            if (regex instanceof RegExp) {
+                return string.match(regex)
+            } else {
+                return string.indexOf(regex) != -1
+            }
+        }, desc)
+    }
+
+    /**
+     * The opposite of like. tests that the string doesn't match the regex.
+     *
+     * @param {string} string
+     * @param {RegExp} regex
+     * @param {string} desc 
+     */
+    unlike(string, regex, desc) {
+        this.#pass_if(function() {
+            return !string.match(regex);
+        }, desc)
+    }
+
+}
+
+/**
+ * Run a test and render a summarization.
+ *
+ * @param {Tap} t
+ * @param {string} testName
+ * @param {function(Tap)} test 
+ */
+function runTest(t, testName, test) {
+    t.comment('running ' + testName + ' tests');
+    try {
+        test(t);
+        summarize(t);
+    }
+    catch (err) {
+        t.comment("Test Suite Crashed!!! (" + err + ")");
+    }
+
+    return t;
+}
+
+/**
+ * Output a summary of the tests as comments.
+ *
+ * @param {Tap} t 
+ */
+function summarize(t) {
+    if (t.planned > t.counter) {
+        t.comment('looks like you planned ' + t.planned + ' tests but only ran '
+            + t.counter + ' tests');
+    } else if (t.planned < t.counter) {
+        t.comment('looks like you planned ' + t.planned + ' tests but ran '
+            + (t.counter - t.planned) + ' tests extra');
+    }
+    t.comment('ran ' + t.counter + ' tests out of ' + t.planned);
+    t.comment('passed ' + t.passed + ' tests out of ' + t.planned);
+    t.comment('failed ' + t.failed + ' tests out of ' + t.planned);
+}
+
+/**
+ * @param {Tap} t
+ * @param {Array<{'plan': Number, name: string, 'test': function(Tap)}} suite 
+ */
+function runSuite(t, suite) {
+    const plan = suite.reduce((acc, item) => {
+        return acc + item.plan
+    }, 0);
+    t.plan(plan);
+    for (var item of suite) {
+        t.comment('running ' + item.name + ' tests');
+        item.test(t);
+    }
+    summarize(t);
+}
+
+export { Tap, runTest, runSuite, summarize, BrowserRenderer, NodeRenderer };
+
diff --git a/tests/Tap.d.js b/tests/Tap.d.js
new file mode 100644
index 0000000..5a5e4a2
--- /dev/null
+++ b/tests/Tap.d.js
@@ -0,0 +1,20 @@
+/** @interface */
+class TapRenderer {
+    /** Renders output for the test results
+     * @param {string} text 
+     */
+    out(text) {
+    }
+
+    /** Diagnostic formatter for TAP Output.
+     *
+     * @param {Array<string>} lines
+     */
+    comment(lines) {
+    }
+}
+
+/**
+ * @typedef TapSuite
+ * @type {Array<{'plan': Number, name: string, 'test': function(Tap)}}
+ */
diff --git a/tests/TapHarness.html b/tests/TapHarness.html
new file mode 100644
index 0000000..9be7ec6
--- /dev/null
+++ b/tests/TapHarness.html
@@ -0,0 +1,44 @@
+<html>
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
+</head>
+<body>
+<style type="text/css">
+.test {
+    margin-top : 10px;
+    margin-bottom : 10px;
+    border : 3px;
+    border-style : inset;
+    overflow : auto;
+}
+
+.small {
+    height : 20px;
+}
+
+.big {
+    height : 600px;
+}
+
+.comment { color: darkgray; }
+.pass { color: green; }
+.fail { color: red; }
+</style>
+<script type="text/javascript">
+    /** Configuration options
+    *
+    */
+    var tests = [
+        '01_tap.t.js',
+    ];
+</script>
+Heracles custom elements test harness.
+<script type="module">
+    import { Tap, runSuite } from './TAP.mjs';
+    import { tapSuite } from './suite.mjs';
+
+    const pair = Tap.Browser();
+    runSuite(pair.Tap, tapSuite);
+</script>
+</body>
+</html>
diff --git a/tests/suite.mjs b/tests/suite.mjs
new file mode 100644
index 0000000..cef896a
--- /dev/null
+++ b/tests/suite.mjs
@@ -0,0 +1,57 @@
+// TODO(jwall): Figure out how to handle the missing browser apis in node contexts.
+import { GraphPlot, SpanSelector } from '../static/lib.mjs';
+
+function deepEqual(got, expected) {
+      // Check if both are the same reference or both are null
+  if (got === expected) { return true; }
+
+  // Check if both are objects (including arrays) and neither is null
+  if (typeof got !== 'object' || got === null ||
+      typeof expected !== 'object' || expected === null) {
+    return false;
+  }
+
+  // Get the keys of both objects
+  const keysGot = Object.keys(got), keysExpected = Object.keys(expected);
+
+  // If number of properties is different, objects are not equivalent
+  if (keysGot.length !== keysExpected.length) { return false; }
+
+  // Check all properties of a are in b and are equal
+  for (let key of keysGot) {
+    if (!keysExpected.includes(key) || !deepEqual(got[key], expected[key])) {  return false; }
+  }
+
+  // If we got this far, objects are considered equivalent
+  return true;
+}
+
+/**
+ * @type {TapSuite}
+ */
+export var tapSuite = [
+    {
+        plan: 2,
+        name: "Custom Element registration Tests",
+        test: function(t) {
+            t.ok(customElements.get(GraphPlot.elementName), `GraphPlot element is registered with name ${GraphPlot.elementName}`);
+            t.ok(customElements.get(SpanSelector.elementName), `SpanSelector element is registered with name ${SpanSelector.elementName}`);
+        }
+    },
+    {
+        plan: 5,
+        name: "PopulateFilterData test",
+        test: function(t) {
+            const plot = new GraphPlot();
+            t.ok(deepEqual(plot.getFilterLabels(), {}), "filter lables start out empty");
+            plot.populateFilterData({});
+            t.ok(typeof(deepEqual(plot.getFilterLabels()), {}), "filter lables are still empty");
+            plot.populateFilterData({"foo": "bar"});
+            t.ok(deepEqual(plot.getFilterLabels(), {"foo": ["bar"]}), "filter labels get set with list of one item on first label");
+            plot.populateFilterData({"foo": "quux"});
+            t.ok(deepEqual(plot.getFilterLabels(), {"foo": ["bar", "quux"]}), "list of two values after second label value");
+            plot.populateFilterData({"foo": "bar"});
+            t.ok(deepEqual(plot.getFilterLabels(), {"foo": ["bar", "quux"]}), "We don't double add the same value");
+        }
+    }
+];