diff --git a/src/runTest.ts b/src/runTest.ts
new file mode 100644
index 0000000..ec0522d
--- /dev/null
+++ b/src/runTest.ts
@@ -0,0 +1,209 @@
+import { type TestInput, type TestOutput } from "./types";
+
+function h(unsafe: string): string {
+  if (unsafe == null) {
+    return "";
+  }
+
+  return unsafe
+    .replace(/&/g, "&")
+    .replace(/</g, "&lt;")
+    .replace(/>/g, "&gt;")
+    .replace(/"/g, "&quot;")
+    .replace(/'/g, "&#039;");
+}
+
+export function runTest(input: TestInput): TestOutput {
+  if (input.regex == null || input.regex.length == 0) {
+    return { success: false, message: "No regex to test!" };
+  }
+
+  const options = input.option ? input.option.join("") : undefined;
+
+  const html = [];
+  html.push(
+    '<table class="table table-bordered table-striped" style="width:auto;">\n'
+  );
+
+  html.push("\t<tr>\n");
+  html.push("\t\t<td>Regular Expression</td>\n");
+  html.push("\t\t<td>");
+  html.push(h(input.regex));
+  html.push("</td>\n");
+  html.push("\t</tr>\n");
+
+  html.push("\t<tr>\n");
+  html.push("\t\t<td>Replacement</td>\n");
+  html.push("\t\t<td>");
+  html.push(h(input.replacement));
+  html.push("</td>\n");
+
+  html.push("\t<tr>\n");
+  html.push("\t\t<td>Options</td>\n");
+  html.push("\t\t<td>");
+  html.push(options ? h(options) : "<i>(none)</i>");
+  html.push("</td>\n");
+  html.push("\t</tr>\n");
+  html.push("</table>\n");
+
+  let compileTest: RegExp;
+
+  try {
+    compileTest = new RegExp(input.regex, options);
+  } catch (err) {
+    const message = err instanceof Error ? err.message : `unknown error ${err}`;
+    return {
+      success: false,
+      message: `unable to create RegExp object: ${message}`,
+      html: html.join(""),
+    };
+  }
+
+  try {
+    html.push('<table class="table table-bordered table-striped">\n');
+
+    html.push("\t<thead>");
+    html.push("\t\t<tr>\n");
+    html.push('\t\t\t<th style="text-align:center;">Test</th>\n');
+    html.push("\t\t\t<th>Input</th>");
+    html.push("\t\t\t<th>regex.test()</th>");
+    html.push("\t\t\t<th>input.replace()</th>");
+    html.push("\t\t\t<th>input.replaceAll()</th>");
+    html.push("\t\t\t<th>input.split()[]</th>");
+    html.push("\t\t\t<th>regex.exec().index</th>");
+    html.push("\t\t\t<th>regex.exec()[]</th>");
+    html.push("\t\t\t<th>regex.lastIndex</th>");
+    html.push("\t\t</tr>\n");
+    html.push("\t</thead>\n");
+    html.push("\t<tbody>\n");
+
+    var count = 0;
+
+    if (input.inputs != null) {
+      for (var loop = 0; loop < input.inputs.length; loop++) {
+        var target = input.inputs[loop];
+
+        if (target.length == 0) {
+          continue;
+        }
+        html.push("\t\t<tr>\n");
+
+        html.push('\t\t\t<td style="text-align:center;">');
+        html.push(loop + 1);
+        html.push("</td>\n");
+
+        html.push("\t\t\t<td>");
+        html.push(h(target));
+        html.push("</td>\n");
+
+        html.push("\t\t\t<td>");
+        html.push(
+          new RegExp(input.regex, options).test(target) ? "true" : "false"
+        );
+        html.push("</td>\n");
+
+        html.push("\t\t\t<td>");
+        html.push(
+          h(target.replace(new RegExp(input.regex, options), input.replacement))
+        );
+        html.push("</td>\n");
+
+        html.push("\t\t\t<td>");
+        try {
+          html.push(
+            h(
+              target.replaceAll(
+                new RegExp(input.regex, options),
+                input.replacement
+              )
+            )
+          );
+        } catch (replaceAllErr) {
+          const message =
+            replaceAllErr instanceof Error
+              ? replaceAllErr.message
+              : `unknown error ${replaceAllErr}`;
+          html.push(`<i>${message}</i>`);
+        }
+        html.push("</td>\n");
+
+        html.push("\t\t\t<td>");
+        var splits = target.split(new RegExp(input.regex, options));
+        for (var split = 0; split < splits.length; split++) {
+          html.push("[");
+          html.push(split);
+          html.push("]: ");
+          html.push(splits[split] == null ? "<i>(null)</i>" : h(splits[split]));
+          html.push("<br/>");
+        }
+        html.push("</td>\n");
+
+        var regex = new RegExp(input.regex, options);
+        var result = regex.exec(target);
+        if (result == null) {
+          html.push('\t\t\t<td colspan="6"><i>(null)</i></td>\n');
+        } else {
+          var first = true;
+
+          while (result != null) {
+            if (first == true) {
+              first = false;
+            } else {
+              html.push("</tr>\n");
+              html.push('\t\t\t<td colspan="6" style="text-align:right;">');
+              html.push("regex.exec()");
+              html.push("</td>\n");
+            }
+
+            html.push("\t\t\t<td>");
+            html.push(result.index);
+            html.push("</td>\n");
+
+            html.push("\t\t\t<td>");
+            for (var capture = 0; capture < result.length; capture++) {
+              html.push("[");
+              html.push(capture);
+              html.push("]: ");
+              html.push(
+                result[capture] == null ? "<i>(null)</i>" : h(result[capture])
+              );
+              html.push("<br/>");
+            }
+            html.push("</td>\n");
+
+            html.push("\t\t\t<td>");
+            html.push(regex.lastIndex);
+            html.push("</td>\n");
+
+            result = global ? regex.exec(target) : null;
+          }
+        }
+        html.push("\t\t</tr>\n");
+        count++;
+      }
+    }
+
+    if (count == 0) {
+      html.push("\t\t<tr>\n");
+      html.push('\t\t<td colspan="8"><i>');
+      html.push("(no input to test)");
+      html.push("</i></td>\n");
+      html.push("\t\t</tr>\n");
+    }
+
+    html.push("\t</tbody>\n");
+    html.push("</table>\n");
+  } catch (err) {
+    const message = err instanceof Error ? err.message : `unknown error ${err}`;
+    return {
+      success: false,
+      message: `unable to run tests: ${message}`,
+      html: html.join(""),
+    };
+  }
+
+  return {
+    success: true,
+    html: html.join(""),
+  };
+}
diff --git a/src/server.ts b/src/server.ts
index 1b517b3..bcc3556 100644
--- a/src/server.ts
+++ b/src/server.ts
@@ -1,4 +1,6 @@
 import type { Server } from "bun";
+import type { TestInput } from "./types";
+import { runTest } from "./runTest";
 
 Bun.serve({
   development: process.env.NODE_ENV !== "production",
@@ -43,7 +45,7 @@ Bun.serve({
 
     return handleJsonp(req, {
       success: false,
-      code: 'ENOTFOUND',
+      code: "ENOTFOUND",
       statusCode: 404,
       message: `Not Found: ${pathname}`,
     });
@@ -69,26 +71,56 @@ function handleJsonp(req: Request, data: Object): Response {
   });
 }
 
-function testJson(req: Request, server: Server): Response {
-  const body = req.body;
+async function testJson(req: Request, server: Server): Promise<Response> {
+  let testInput: TestInput;
 
-  return handleJsonp(req, {
-    sucess: false,
-    html: `<div class="alert alert-danger" role="alert">Bun support is not finished yet</div>`,
-  });
+  if (req.method === "POST") {
+    if (req.headers.get("content-type") === "application/json") {
+      testInput = await req.json();
+    } else {
+      const data = await req.formData();
+      console.log("formData", data);
+
+      testInput = {
+        engine: "bun",
+        regex: data.get("regex") as string,
+        replacement: data.get("replacement") as string,
+        option: data.getAll("option") as string[],
+        inputs: data.getAll("input") as string[],
+      };
+    }
+  } else {
+    const searchParams = new URL(req.url).searchParams;
+    testInput = {
+      engine: searchParams.get("engine") || "bun",
+      regex: searchParams.get("regex") || "",
+      replacement: searchParams.get("replacement") || "",
+      option: searchParams.getAll("option") as string[],
+      inputs: searchParams.getAll("input") as string[],
+    };
+    console.log("searchParams", searchParams);
+  }
+
+  console.log("testInput", testInput);
+
+  const retVal = runTest(testInput);
+
+  console.log("testOutput", retVal);
+
+  return handleJsonp(req, retVal);
 }
 
 function statusJson(req: Request, server: Server): Response {
   const retVal = {
     success: true,
     tech: `Bun v${Bun.version}`,
-    lastmod: process.env.LASTMOD || '(not set)',
-    commit: process.env.COMMIT || '(not set)',
+    lastmod: process.env.LASTMOD || "(not set)",
+    commit: process.env.COMMIT || "(not set)",
     timestamp: new Date().toISOString(),
     version: `${Bun.version}`,
     revision: `${Bun.revision}`,
-    'process.arch': process.arch,
-    'process.platform': process.platform,
+    "process.arch": process.arch,
+    "process.platform": process.platform,
   };
 
   return handleJsonp(req, retVal);
diff --git a/src/types.ts b/src/types.ts
new file mode 100644
index 0000000..c892e4b
--- /dev/null
+++ b/src/types.ts
@@ -0,0 +1,16 @@
+
+
+export type TestInput = {
+  engine: string;
+  regex: string;
+  replacement: string;
+  extras?: string[];
+  option: string[];
+  inputs: string[];
+};
+
+export type TestOutput = {
+  success: boolean;
+  html?: string;
+  message?: string;
+};
\ No newline at end of file