diff --git a/Dockerfile b/Dockerfile
deleted file mode 100644
index d742df8..0000000
--- a/Dockerfile
+++ /dev/null
@@ -1,16 +0,0 @@
-FROM node:10-alpine
-
-LABEL "com.github.actions.name"="Create an issue"
-LABEL "com.github.actions.description"="Creates a new issue using a template with front matter."
-LABEL "com.github.actions.icon"="alert-circle"
-LABEL "com.github.actions.color"="gray-dark"
-
-LABEL "repository"="https://github.com/JasonEtco/create-an-issue"
-LABEL "homepage"="https://github.com/JasonEtco/create-an-issue"
-LABEL "maintainer"="Jason Etcovitch <jasonetco@github.com>"
-
-COPY package*.json ./
-RUN npm ci
-COPY . .
-
-ENTRYPOINT ["node", "/index.js"]
diff --git a/codecov.yml b/codecov.yml
index 477ee9f..beddfc0 100644
--- a/codecov.yml
+++ b/codecov.yml
@@ -8,4 +8,4 @@ coverage:
       default:
         threshold: 3
 
-comment: false
\ No newline at end of file
+comment: false
diff --git a/package-lock.json b/package-lock.json
index 359b423..f60f99d 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -12,7 +12,8 @@
         "front-matter": "^4.0.2",
         "js-yaml": "^4.1.0",
         "nunjucks": "^3.2.3",
-        "nunjucks-date-filter": "^0.1.1"
+        "nunjucks-date-filter": "^0.1.1",
+        "zod": "^3.20.2"
       },
       "devDependencies": {
         "@tsconfig/node12": "^1.0.11",
@@ -5601,6 +5602,14 @@
       "funding": {
         "url": "https://github.com/sponsors/sindresorhus"
       }
+    },
+    "node_modules/zod": {
+      "version": "3.20.2",
+      "resolved": "https://registry.npmjs.org/zod/-/zod-3.20.2.tgz",
+      "integrity": "sha512-1MzNQdAvO+54H+EaK5YpyEy0T+Ejo/7YLHS93G3RnYWh5gaotGHwGeN/ZO687qEDU2y4CdStQYXVHIgrUl5UVQ==",
+      "funding": {
+        "url": "https://github.com/sponsors/colinhacks"
+      }
     }
   }
 }
diff --git a/package.json b/package.json
index d994823..a8f8bf4 100644
--- a/package.json
+++ b/package.json
@@ -15,7 +15,8 @@
     "front-matter": "^4.0.2",
     "js-yaml": "^4.1.0",
     "nunjucks": "^3.2.3",
-    "nunjucks-date-filter": "^0.1.1"
+    "nunjucks-date-filter": "^0.1.1",
+    "zod": "^3.20.2"
   },
   "devDependencies": {
     "@tsconfig/node12": "^1.0.11",
diff --git a/src/action.ts b/src/action.ts
index 3e7fae5..1319df9 100644
--- a/src/action.ts
+++ b/src/action.ts
@@ -1,113 +1,155 @@
-import * as core from '@actions/core'
-import { Toolkit } from 'actions-toolkit'
-import fm from 'front-matter'
-import nunjucks from 'nunjucks'
-// @ts-ignore
-import dateFilter from 'nunjucks-date-filter'
-import { FrontMatterAttributes, listToArray, setOutputs } from './helpers'
-
-function logError(tools: Toolkit, template: string, action: 'creating' | 'updating', err: any) {
+import * as core from "@actions/core";
+import { Toolkit } from "actions-toolkit";
+import fm from "front-matter";
+import nunjucks from "nunjucks";
+// @ts-expect-error
+import dateFilter from "nunjucks-date-filter";
+import { ZodError } from "zod";
+import {
+  FrontMatterAttributes,
+  frontmatterSchema,
+  listToArray,
+  setOutputs,
+} from "./helpers";
+
+function logError(
+  tools: Toolkit,
+  template: string,
+  action: "creating" | "updating" | "parsing",
+  err: any
+) {
   // Log the error message
-  const errorMessage = `An error occurred while ${action} the issue. This might be caused by a malformed issue title, or a typo in the labels or assignees. Check ${template}!`
-  tools.log.error(errorMessage)
-  tools.log.error(err)
+  const errorMessage = `An error occurred while ${action} the issue. This might be caused by a malformed issue title, or a typo in the labels or assignees. Check ${template}!`;
+  tools.log.error(errorMessage);
+  tools.log.error(err);
 
   // The error might have more details
-  if (err.errors) tools.log.error(err.errors)
+  if (err.errors) tools.log.error(err.errors);
 
   // Exit with a failing status
-  core.setFailed(errorMessage + '\n\n' + err.message)
-  return tools.exit.failure()
+  core.setFailed(errorMessage + "\n\n" + err.message);
+  return tools.exit.failure();
 }
 
-export async function createAnIssue (tools: Toolkit) {
-  const template = tools.inputs.filename || '.github/ISSUE_TEMPLATE.md'
-  const assignees = tools.inputs.assignees
+export async function createAnIssue(tools: Toolkit) {
+  const template = tools.inputs.filename || ".github/ISSUE_TEMPLATE.md";
+  const assignees = tools.inputs.assignees;
 
-  let updateExisting: Boolean | null = null
+  let updateExisting: Boolean | null = null;
   if (tools.inputs.update_existing) {
-    if (tools.inputs.update_existing === 'true') {
-      updateExisting = true
-    } else if (tools.inputs.update_existing === 'false') {
-      updateExisting = false
+    if (tools.inputs.update_existing === "true") {
+      updateExisting = true;
+    } else if (tools.inputs.update_existing === "false") {
+      updateExisting = false;
     } else {
-      tools.exit.failure(`Invalid value update_existing=${tools.inputs.update_existing}, must be one of true or false`)
+      tools.exit.failure(
+        `Invalid value update_existing=${tools.inputs.update_existing}, must be one of true or false`
+      );
     }
   }
 
-  const env = nunjucks.configure({ autoescape: false })
-  env.addFilter('date', dateFilter)
+  const env = nunjucks.configure({ autoescape: false });
+  env.addFilter("date", dateFilter);
 
   const templateVariables = {
     ...tools.context,
     repo: tools.context.repo,
     env: process.env,
-    date: Date.now()
-  }
+    date: Date.now(),
+  };
 
   // Get the file
-  tools.log.debug('Reading from file', template)
-  const file = await tools.readFile(template) as string
+  tools.log.debug("Reading from file", template);
+  const file = (await tools.readFile(template)) as string;
 
   // Grab the front matter as JSON
-  const { attributes, body } = fm<FrontMatterAttributes>(file)
-  tools.log(`Front matter for ${template} is`, attributes)
+  const { attributes: rawAttributes, body } = fm<FrontMatterAttributes>(file);
+
+  let attributes: FrontMatterAttributes;
+  try {
+    attributes = await frontmatterSchema.parseAsync(rawAttributes);
+  } catch (err) {
+    if (err instanceof ZodError) {
+      const formatted = err.format();
+      return logError(tools, template, "parsing", formatted);
+    }
+    throw err;
+  }
+
+  tools.log(`Front matter for ${template} is`, attributes);
 
   const templated = {
     body: env.renderString(body, templateVariables),
-    title: env.renderString(attributes.title, templateVariables)
-  }
-  tools.log.debug('Templates compiled', templated)
+    title: env.renderString(attributes.title, templateVariables),
+  };
+  tools.log.debug("Templates compiled", templated);
 
   if (updateExisting !== null) {
-    tools.log.info(`Fetching issues with title "${templated.title}"`)
+    tools.log.info(`Fetching issues with title "${templated.title}"`);
 
-    let query = `is:issue repo:${process.env.GITHUB_REPOSITORY} in:title "${templated.title.replace(/['"]/g, "\\$&")}"`
+    let query = `is:issue repo:${
+      process.env.GITHUB_REPOSITORY
+    } in:title "${templated.title.replace(/['"]/g, "\\$&")}"`;
 
-    const searchExistingType = tools.inputs.search_existing || 'open'
-    const allowedStates = ['open', 'closed']
+    const searchExistingType = tools.inputs.search_existing || "open";
+    const allowedStates = ["open", "closed"];
     if (allowedStates.includes(searchExistingType)) {
-      query += ` is:${searchExistingType}`
+      query += ` is:${searchExistingType}`;
     }
 
-    const existingIssues = await tools.github.search.issuesAndPullRequests({ q: query })
-    const existingIssue = existingIssues.data.items.find(issue => issue.title === templated.title)
+    const existingIssues = await tools.github.search.issuesAndPullRequests({
+      q: query,
+    });
+    const existingIssue = existingIssues.data.items.find(
+      (issue) => issue.title === templated.title
+    );
     if (existingIssue) {
       if (updateExisting === false) {
-        tools.exit.success(`Existing issue ${existingIssue.title}#${existingIssue.number}: ${existingIssue.html_url} found but not updated`)
+        tools.exit.success(
+          `Existing issue ${existingIssue.title}#${existingIssue.number}: ${existingIssue.html_url} found but not updated`
+        );
       } else {
         try {
-          tools.log.info(`Updating existing issue ${existingIssue.title}#${existingIssue.number}: ${existingIssue.html_url}`)
+          tools.log.info(
+            `Updating existing issue ${existingIssue.title}#${existingIssue.number}: ${existingIssue.html_url}`
+          );
           const issue = await tools.github.issues.update({
             ...tools.context.repo,
             issue_number: existingIssue.number,
-            body: templated.body
-          })
-          setOutputs(tools, issue.data)
-          tools.exit.success(`Updated issue ${existingIssue.title}#${existingIssue.number}: ${existingIssue.html_url}`)
+            body: templated.body,
+          });
+          setOutputs(tools, issue.data);
+          tools.exit.success(
+            `Updated issue ${existingIssue.title}#${existingIssue.number}: ${existingIssue.html_url}`
+          );
         } catch (err: any) {
-          return logError(tools, template, 'updating', err)
+          return logError(tools, template, "updating", err);
         }
       }
     } else {
-      tools.log.info('No existing issue found to update')
+      tools.log.info("No existing issue found to update");
     }
   }
 
   // Create the new issue
-  tools.log.info(`Creating new issue ${templated.title}`)
+  tools.log.info(`Creating new issue ${templated.title}`);
   try {
     const issue = await tools.github.issues.create({
       ...tools.context.repo,
       ...templated,
-      assignees: assignees ? listToArray(assignees) : listToArray(attributes.assignees),
+      assignees: assignees
+        ? listToArray(assignees)
+        : listToArray(attributes.assignees),
       labels: listToArray(attributes.labels),
-      milestone: Number(tools.inputs.milestone || attributes.milestone) || undefined
-    })
-
-    setOutputs(tools, issue.data)
-    tools.log.success(`Created issue ${issue.data.title}#${issue.data.number}: ${issue.data.html_url}`)
+      milestone:
+        Number(tools.inputs.milestone || attributes.milestone) || undefined,
+    });
+
+    setOutputs(tools, issue.data);
+    tools.log.success(
+      `Created issue ${issue.data.title}#${issue.data.number}: ${issue.data.html_url}`
+    );
   } catch (err: any) {
-    return logError(tools, template, 'creating', err)
+    return logError(tools, template, "creating", err);
   }
 }
diff --git a/src/helpers.ts b/src/helpers.ts
index 31134b4..8444a9c 100644
--- a/src/helpers.ts
+++ b/src/helpers.ts
@@ -1,18 +1,26 @@
-import { Toolkit } from 'actions-toolkit'
+import { Toolkit } from "actions-toolkit";
+import { z } from "zod";
 
-export interface FrontMatterAttributes {
-  title: string
-  assignees?: string[] | string
-  labels?: string[] | string
-  milestone?: string | number
-}
+export const frontmatterSchema = z
+  .object({
+    title: z.string(),
+    assignees: z.union([z.array(z.string()), z.string()]).optional(),
+    labels: z.union([z.array(z.string()), z.string()]).optional(),
+    milestone: z.union([z.string(), z.number()]).optional(),
+  })
+  .strict();
+
+export type FrontMatterAttributes = z.infer<typeof frontmatterSchema>;
 
-export function setOutputs (tools: Toolkit, issue: { number: number, html_url: string }) {
-  tools.outputs.number = String(issue.number)
-  tools.outputs.url = issue.html_url
+export function setOutputs(
+  tools: Toolkit,
+  issue: { number: number; html_url: string }
+) {
+  tools.outputs.number = String(issue.number);
+  tools.outputs.url = issue.html_url;
 }
 
-export function listToArray (list?: string[] | string) {
-  if (!list) return []
-  return Array.isArray(list) ? list : list.split(', ')
-}
\ No newline at end of file
+export function listToArray(list?: string[] | string) {
+  if (!list) return [];
+  return Array.isArray(list) ? list : list.split(", ");
+}
diff --git a/src/index.ts b/src/index.ts
index 0fdcadd..f78c0fc 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,6 +1,6 @@
-import { Toolkit } from 'actions-toolkit'
-import { createAnIssue } from './action'
+import { Toolkit } from "actions-toolkit";
+import { createAnIssue } from "./action";
 
 Toolkit.run(createAnIssue, {
-  secrets: ['GITHUB_TOKEN']
-})
+  secrets: ["GITHUB_TOKEN"],
+});
diff --git a/tests/__snapshots__/index.test.ts.snap b/tests/__snapshots__/index.test.ts.snap
index 5172e45..7340d64 100644
--- a/tests/__snapshots__/index.test.ts.snap
+++ b/tests/__snapshots__/index.test.ts.snap
@@ -232,6 +232,32 @@ exports[`create-an-issue logs a helpful error if creating an issue throws an err
 ]
 `;
 
+exports[`create-an-issue logs a helpful error if the frontmatter is invalid 1`] = `
+[
+  [
+    "An error occurred while parsing the issue. This might be caused by a malformed issue title, or a typo in the labels or assignees. Check .github/invalid-frontmatter.md!",
+  ],
+  [
+    {
+      "_errors": [
+        "Unrecognized key(s) in object: 'name', 'not_a_thing'",
+      ],
+      "labels": {
+        "_errors": [
+          "Expected array, received number",
+          "Expected string, received number",
+        ],
+      },
+      "title": {
+        "_errors": [
+          "Required",
+        ],
+      },
+    },
+  ],
+]
+`;
+
 exports[`create-an-issue logs a helpful error if updating an issue throws an error with more errors 1`] = `
 [
   [
diff --git a/tests/fixtures/.github/invalid-frontmatter.md b/tests/fixtures/.github/invalid-frontmatter.md
new file mode 100644
index 0000000..ab948e6
--- /dev/null
+++ b/tests/fixtures/.github/invalid-frontmatter.md
@@ -0,0 +1,6 @@
+---
+name: "Not a title"
+labels: 123
+not_a_thing: "testing"
+---
+Hi!
\ No newline at end of file
diff --git a/tests/fixtures/event.json b/tests/fixtures/event.json
index d2bf5c4..85ef91e 100644
--- a/tests/fixtures/event.json
+++ b/tests/fixtures/event.json
@@ -1,6 +1,8 @@
 {
   "repository": {
-    "owner": { "login": "JasonEtco" },
+    "owner": {
+      "login": "JasonEtco"
+    },
     "name": "waddup"
   }
-}
+}
\ No newline at end of file
diff --git a/tests/index.test.ts b/tests/index.test.ts
index 2e95f2a..6db1df5 100644
--- a/tests/index.test.ts
+++ b/tests/index.test.ts
@@ -1,305 +1,338 @@
-import nock from 'nock'
-import * as core from '@actions/core'
-import { Toolkit } from 'actions-toolkit'
-import { Signale } from 'signale'
-import { createAnIssue } from '../src/action'
+import nock from "nock";
+import * as core from "@actions/core";
+import { Toolkit } from "actions-toolkit";
+import { Signale } from "signale";
+import { createAnIssue } from "../src/action";
 
 function generateToolkit() {
   const tools = new Toolkit({
-    logger: new Signale({ disabled: true })
-  })
+    logger: new Signale({ disabled: true }),
+  });
 
-  jest.spyOn(tools.log, 'info')
-  jest.spyOn(tools.log, 'error')
-  jest.spyOn(tools.log, 'success')
+  jest.spyOn(tools.log, "info");
+  jest.spyOn(tools.log, "error");
+  jest.spyOn(tools.log, "success");
 
   // Turn core.setOutput into a mocked noop
-  jest.spyOn(core, 'setOutput')
-    .mockImplementation(() => {})
+  jest.spyOn(core, "setOutput").mockImplementation(() => {});
 
   // Turn core.setFailed into a mocked noop
-  jest.spyOn(core, 'setFailed')
-    .mockImplementation(() => {})
+  jest.spyOn(core, "setFailed").mockImplementation(() => {});
 
-  tools.exit.success = jest.fn() as any
-  tools.exit.failure = jest.fn() as any
+  tools.exit.success = jest.fn() as any;
+  tools.exit.failure = jest.fn() as any;
 
-  return tools
+  return tools;
 }
 
-describe('create-an-issue', () => {
-  let tools: Toolkit
-  let params: any
+describe("create-an-issue", () => {
+  let tools: Toolkit;
+  let params: any;
 
   beforeEach(() => {
-    nock('https://api.github.com')
-      .post(/\/repos\/.*\/.*\/issues/).reply(200, (_, body: any) => {
-        params = body
+    nock("https://api.github.com")
+      .post(/\/repos\/.*\/.*\/issues/)
+      .reply(200, (_, body: any) => {
+        params = body;
         return {
           title: body.title,
           number: 1,
-          html_url: 'www'
-        }
-      })
+          html_url: "www",
+        };
+      });
 
-    tools = generateToolkit()
+    tools = generateToolkit();
 
     // Ensure that the filename input isn't set at the start of a test
-    delete process.env.INPUT_FILENAME
+    delete process.env.INPUT_FILENAME;
 
     // Simulate an environment variable added for the action
-    process.env.EXAMPLE = 'foo'
-  })
+    process.env.EXAMPLE = "foo";
+  });
 
-  it('creates a new issue', async () => {
-    await createAnIssue(tools)
-    expect(params).toMatchSnapshot()
-    expect(tools.log.success).toHaveBeenCalled()
-    expect((tools.log.success as any).mock.calls).toMatchSnapshot()
+  it("creates a new issue", async () => {
+    await createAnIssue(tools);
+    expect(params).toMatchSnapshot();
+    expect(tools.log.success).toHaveBeenCalled();
+    expect((tools.log.success as any).mock.calls).toMatchSnapshot();
 
     // Verify that the outputs were set
-    expect(core.setOutput).toHaveBeenCalledTimes(2)
-    expect(core.setOutput).toHaveBeenCalledWith('url', 'www')
-    expect(core.setOutput).toHaveBeenCalledWith('number', '1')
-  })
-
-  it('creates a new issue from a different template', async () => {
-    process.env.INPUT_FILENAME = '.github/different-template.md'
-    tools.context.payload = { repository: { owner: { login: 'JasonEtco' }, name: 'waddup' } }
-    await createAnIssue(tools)
-    expect(params).toMatchSnapshot()
-    expect(tools.log.success).toHaveBeenCalled()
-    expect((tools.log.success as any).mock.calls).toMatchSnapshot()
-  })
-
-  it('creates a new issue with some template variables', async () => {
-    process.env.INPUT_FILENAME = '.github/variables.md'
-    await createAnIssue(tools)
-    expect(params).toMatchSnapshot()
-    expect(tools.log.success).toHaveBeenCalled()
-    expect((tools.log.success as any).mock.calls).toMatchSnapshot()
-  })
-
-  it('creates a new issue with the context.repo template variables', async () => {
-    process.env.INPUT_FILENAME = '.github/context-repo-template.md'
-    await createAnIssue(tools)
-    expect(params).toMatchSnapshot()
-    expect(tools.log.success).toHaveBeenCalled()
-    expect((tools.log.success as any).mock.calls).toMatchSnapshot()
-  })
-
-  it('creates a new issue with assignees, labels and a milestone', async () => {
-    process.env.INPUT_FILENAME = '.github/kitchen-sink.md'
-    await createAnIssue(tools)
-    expect(params).toMatchSnapshot()
-    expect(tools.log.success).toHaveBeenCalled()
-    expect((tools.log.success as any).mock.calls).toMatchSnapshot()
-  })
-
-  it('creates a new issue with assignees and labels as comma-delimited strings', async () => {
-    process.env.INPUT_FILENAME = '.github/split-strings.md'
-    await createAnIssue(tools)
-    expect(params).toMatchSnapshot()
-    expect(tools.log.success).toHaveBeenCalled()
-    expect((tools.log.success as any).mock.calls).toMatchSnapshot()
-  })
-
-  it('creates a new issue with an assignee passed by input', async () => {
-    process.env.INPUT_ASSIGNEES = 'octocat'
-    await createAnIssue(tools)
-    expect(params).toMatchSnapshot()
-    expect(tools.log.success).toHaveBeenCalled()
-    expect((tools.log.success as any).mock.calls).toMatchSnapshot()
-  })
-
-  it('creates a new issue with multiple assignees passed by input', async () => {
-    process.env.INPUT_ASSIGNEES = 'octocat, JasonEtco'
-    await createAnIssue(tools)
-    expect(params).toMatchSnapshot()
-    expect(tools.log.success).toHaveBeenCalled()
-    expect((tools.log.success as any).mock.calls).toMatchSnapshot()
-  })
-
-  it('creates a new issue with a milestone passed by input', async () => {
-    process.env.INPUT_MILESTONE = '1'
-    await createAnIssue(tools)
-    expect(params).toMatchSnapshot()
-    expect(params.milestone).toBe(1)
-    expect(tools.log.success).toHaveBeenCalled()
-  })
-
-  it('creates a new issue when updating existing issues is enabled but no issues with the same title exist', async () => {
-    nock.cleanAll()
-    nock('https://api.github.com')
-      .get(/\/search\/issues.*/).reply(200, {
-        items: []
+    expect(core.setOutput).toHaveBeenCalledTimes(2);
+    expect(core.setOutput).toHaveBeenCalledWith("url", "www");
+    expect(core.setOutput).toHaveBeenCalledWith("number", "1");
+  });
+
+  it("creates a new issue from a different template", async () => {
+    process.env.INPUT_FILENAME = ".github/different-template.md";
+    tools.context.payload = {
+      repository: { owner: { login: "JasonEtco" }, name: "waddup" },
+    };
+    await createAnIssue(tools);
+    expect(params).toMatchSnapshot();
+    expect(tools.log.success).toHaveBeenCalled();
+    expect((tools.log.success as any).mock.calls).toMatchSnapshot();
+  });
+
+  it("creates a new issue with some template variables", async () => {
+    process.env.INPUT_FILENAME = ".github/variables.md";
+    await createAnIssue(tools);
+    expect(params).toMatchSnapshot();
+    expect(tools.log.success).toHaveBeenCalled();
+    expect((tools.log.success as any).mock.calls).toMatchSnapshot();
+  });
+
+  it("creates a new issue with the context.repo template variables", async () => {
+    process.env.INPUT_FILENAME = ".github/context-repo-template.md";
+    await createAnIssue(tools);
+    expect(params).toMatchSnapshot();
+    expect(tools.log.success).toHaveBeenCalled();
+    expect((tools.log.success as any).mock.calls).toMatchSnapshot();
+  });
+
+  it("creates a new issue with assignees, labels and a milestone", async () => {
+    process.env.INPUT_FILENAME = ".github/kitchen-sink.md";
+    await createAnIssue(tools);
+    expect(params).toMatchSnapshot();
+    expect(tools.log.success).toHaveBeenCalled();
+    expect((tools.log.success as any).mock.calls).toMatchSnapshot();
+  });
+
+  it("creates a new issue with assignees and labels as comma-delimited strings", async () => {
+    process.env.INPUT_FILENAME = ".github/split-strings.md";
+    await createAnIssue(tools);
+    expect(params).toMatchSnapshot();
+    expect(tools.log.success).toHaveBeenCalled();
+    expect((tools.log.success as any).mock.calls).toMatchSnapshot();
+  });
+
+  it("creates a new issue with an assignee passed by input", async () => {
+    process.env.INPUT_ASSIGNEES = "octocat";
+    await createAnIssue(tools);
+    expect(params).toMatchSnapshot();
+    expect(tools.log.success).toHaveBeenCalled();
+    expect((tools.log.success as any).mock.calls).toMatchSnapshot();
+  });
+
+  it("creates a new issue with multiple assignees passed by input", async () => {
+    process.env.INPUT_ASSIGNEES = "octocat, JasonEtco";
+    await createAnIssue(tools);
+    expect(params).toMatchSnapshot();
+    expect(tools.log.success).toHaveBeenCalled();
+    expect((tools.log.success as any).mock.calls).toMatchSnapshot();
+  });
+
+  it("creates a new issue with a milestone passed by input", async () => {
+    process.env.INPUT_MILESTONE = "1";
+    await createAnIssue(tools);
+    expect(params).toMatchSnapshot();
+    expect(params.milestone).toBe(1);
+    expect(tools.log.success).toHaveBeenCalled();
+  });
+
+  it("creates a new issue when updating existing issues is enabled but no issues with the same title exist", async () => {
+    nock.cleanAll();
+    nock("https://api.github.com")
+      .get(/\/search\/issues.*/)
+      .reply(200, {
+        items: [],
       })
-      .post(/\/repos\/.*\/.*\/issues/).reply(200, (_, body: any) => {
-        params = body
+      .post(/\/repos\/.*\/.*\/issues/)
+      .reply(200, (_, body: any) => {
+        params = body;
         return {
           title: body.title,
           number: 1,
-          html_url: 'www'
-        }
-      })
-
-    process.env.INPUT_UPDATE_EXISTING = 'true'
-
-    await createAnIssue(tools)
-    expect(params).toMatchSnapshot()
-    expect(tools.log.info).toHaveBeenCalledWith('No existing issue found to update')
-    expect(tools.log.success).toHaveBeenCalled()
-  })
-
-  it('updates an existing open issue with the same title', async () => {
-    nock.cleanAll()
-    nock('https://api.github.com')
+          html_url: "www",
+        };
+      });
+
+    process.env.INPUT_UPDATE_EXISTING = "true";
+
+    await createAnIssue(tools);
+    expect(params).toMatchSnapshot();
+    expect(tools.log.info).toHaveBeenCalledWith(
+      "No existing issue found to update"
+    );
+    expect(tools.log.success).toHaveBeenCalled();
+  });
+
+  it("updates an existing open issue with the same title", async () => {
+    nock.cleanAll();
+    nock("https://api.github.com")
       .get(/\/search\/issues.*/)
-      .query(parsedQuery => {
-        const q = parsedQuery['q']
-        if (typeof(q) === 'string') {
-          const args = q.split(' ')
-          return (args.includes('is:open') || args.includes('is:closed')) 
-            && args.includes('is:issue')
+      .query((parsedQuery) => {
+        const q = parsedQuery["q"];
+        if (typeof q === "string") {
+          const args = q.split(" ");
+          return (
+            (args.includes("is:open") || args.includes("is:closed")) &&
+            args.includes("is:issue")
+          );
         } else {
-          return false
+          return false;
         }
       })
       .reply(200, {
-        items: [{ number: 1, title: 'Hello!' }]
+        items: [{ number: 1, title: "Hello!" }],
       })
-      .patch(/\/repos\/.*\/.*\/issues\/.*/).reply(200, {})
+      .patch(/\/repos\/.*\/.*\/issues\/.*/)
+      .reply(200, {});
 
-    process.env.INPUT_UPDATE_EXISTING = 'true'
+    process.env.INPUT_UPDATE_EXISTING = "true";
 
-    await createAnIssue(tools)
-    expect(params).toMatchSnapshot()
-    expect(tools.exit.success).toHaveBeenCalled()
-  })
+    await createAnIssue(tools);
+    expect(params).toMatchSnapshot();
+    expect(tools.exit.success).toHaveBeenCalled();
+  });
 
-  it('escapes quotes in the search query', async () => {
-    process.env.INPUT_FILENAME = '.github/quotes-in-title.md'
+  it("escapes quotes in the search query", async () => {
+    process.env.INPUT_FILENAME = ".github/quotes-in-title.md";
 
-    nock.cleanAll()
-    nock('https://api.github.com')
+    nock.cleanAll();
+    nock("https://api.github.com")
       .get(/\/search\/issues.*/)
-      .query(parsedQuery => {
-        const q = parsedQuery['q'] as string
-        return q.includes('"This title \\\"has quotes\\\""')
+      .query((parsedQuery) => {
+        const q = parsedQuery["q"] as string;
+        return q.includes('"This title \\"has quotes\\""');
       })
       .reply(200, {
-        items: [{ number: 1, title: 'Hello!' }]
+        items: [{ number: 1, title: "Hello!" }],
       })
-      .post(/\/repos\/.*\/.*\/issues/).reply(200, {})
-
-    await createAnIssue(tools)
-    expect(tools.log.success).toHaveBeenCalled()
-  })
-  
-  it('checks the value of update_existing', async () => {
-    process.env.INPUT_UPDATE_EXISTING = 'invalid'
-
-    await createAnIssue(tools)
-    expect(params).toMatchSnapshot()
-    expect(tools.exit.failure).toHaveBeenCalledWith('Invalid value update_existing=invalid, must be one of true or false')
-  })
-
-  it('updates an existing closed issue with the same title', async () => {
-    nock.cleanAll()
-    nock('https://api.github.com')
+      .post(/\/repos\/.*\/.*\/issues/)
+      .reply(200, {});
+
+    await createAnIssue(tools);
+    expect(tools.log.success).toHaveBeenCalled();
+  });
+
+  it("checks the value of update_existing", async () => {
+    process.env.INPUT_UPDATE_EXISTING = "invalid";
+
+    await createAnIssue(tools);
+    expect(params).toMatchSnapshot();
+    expect(tools.exit.failure).toHaveBeenCalledWith(
+      "Invalid value update_existing=invalid, must be one of true or false"
+    );
+  });
+
+  it("updates an existing closed issue with the same title", async () => {
+    nock.cleanAll();
+    nock("https://api.github.com")
       .get(/\/search\/issues.*/)
-      .query(parsedQuery => {
-        const q = parsedQuery['q']
-        if (typeof(q) === 'string') {
-          const args = q.split(' ')
-          return !args.includes('is:all') && args.includes('is:issue')
+      .query((parsedQuery) => {
+        const q = parsedQuery["q"];
+        if (typeof q === "string") {
+          const args = q.split(" ");
+          return !args.includes("is:all") && args.includes("is:issue");
         } else {
-          return false
+          return false;
         }
       })
       .reply(200, {
-        items: [{ number: 1, title: 'Hello!', html_url: '/issues/1' }]
+        items: [{ number: 1, title: "Hello!", html_url: "/issues/1" }],
       })
-      .patch(/\/repos\/.*\/.*\/issues\/.*/).reply(200, {})
-
-    process.env.INPUT_UPDATE_EXISTING = 'true'
-    process.env.INPUT_SEARCH_EXISTING = 'all'
-
-    await createAnIssue(tools)
-    expect(tools.exit.success).toHaveBeenCalledWith('Updated issue Hello!#1: /issues/1')
-  })
+      .patch(/\/repos\/.*\/.*\/issues\/.*/)
+      .reply(200, {});
 
-  it('finds, but does not update an existing issue with the same title', async () => {
-    nock.cleanAll()
-    nock('https://api.github.com')
-      .get(/\/search\/issues.*/).reply(200, {
-        items: [{ number: 1, title: 'Hello!', html_url: '/issues/1' }]
-      })
-    process.env.INPUT_UPDATE_EXISTING = 'false'
-
-    await createAnIssue(tools)
-    expect(params).toMatchSnapshot()
-    expect(tools.exit.success).toHaveBeenCalledWith('Existing issue Hello!#1: /issues/1 found but not updated')
-  })
-
-  it('exits when updating an issue fails', async () => {
-    nock.cleanAll()
-    nock('https://api.github.com')
-      .get(/\/search\/issues.*/).reply(200, {
-        items: [{ number: 1, title: 'Hello!', html_url: '/issues/1' }]
-      })
-      .patch(/\/repos\/.*\/.*\/issues\/.*/).reply(500, {
-        message: 'Updating issue failed'
-      })
+    process.env.INPUT_UPDATE_EXISTING = "true";
+    process.env.INPUT_SEARCH_EXISTING = "all";
 
-    await createAnIssue(tools)
-    expect(tools.exit.failure).toHaveBeenCalled()
-  })
+    await createAnIssue(tools);
+    expect(tools.exit.success).toHaveBeenCalledWith(
+      "Updated issue Hello!#1: /issues/1"
+    );
+  });
 
-  it('logs a helpful error if creating an issue throws an error', async () => {
-    nock.cleanAll()
-    nock('https://api.github.com')
-      .get(/\/search\/issues.*/).reply(200, { items:[] })
-      .post(/\/repos\/.*\/.*\/issues/).reply(500, {
-        message: 'Validation error'
-      })
-
-    await createAnIssue(tools)
-    expect(tools.log.error).toHaveBeenCalled()
-    expect((tools.log.error as any).mock.calls).toMatchSnapshot()
-    expect(tools.exit.failure).toHaveBeenCalled()
-  })
-
-  it('logs a helpful error if creating an issue throws an error with more errors', async () => {
-    nock.cleanAll()
-    nock('https://api.github.com')
-      .get(/\/search\/issues.*/).reply(200, { items:[] })
-      .post(/\/repos\/.*\/.*\/issues/).reply(500, {
-        message: 'Validation error',
-        errors: [{ foo: true }]
-      })
-
-    await createAnIssue(tools)
-    expect(tools.log.error).toHaveBeenCalled()
-    expect((tools.log.error as any).mock.calls).toMatchSnapshot()
-    expect(tools.exit.failure).toHaveBeenCalled()
-  })
-
-  it('logs a helpful error if updating an issue throws an error with more errors', async () => {
-    nock.cleanAll()
-    nock('https://api.github.com')
+  it("finds, but does not update an existing issue with the same title", async () => {
+    nock.cleanAll();
+    nock("https://api.github.com")
+      .get(/\/search\/issues.*/)
+      .reply(200, {
+        items: [{ number: 1, title: "Hello!", html_url: "/issues/1" }],
+      });
+    process.env.INPUT_UPDATE_EXISTING = "false";
+
+    await createAnIssue(tools);
+    expect(params).toMatchSnapshot();
+    expect(tools.exit.success).toHaveBeenCalledWith(
+      "Existing issue Hello!#1: /issues/1 found but not updated"
+    );
+  });
+
+  it("exits when updating an issue fails", async () => {
+    nock.cleanAll();
+    nock("https://api.github.com")
       .get(/\/search\/issues.*/)
-      .reply(200, { items: [{ number: 1, title: 'Hello!' }] })
-      .patch(/\/repos\/.*\/.*\/issues\/.*/).reply(500, {
-        message: 'Validation error',
-        errors: [{ foo: true }]
+      .reply(200, {
+        items: [{ number: 1, title: "Hello!", html_url: "/issues/1" }],
       })
-
-    process.env.INPUT_UPDATE_EXISTING = 'true'
-
-    await createAnIssue(tools)
-    expect(tools.log.error).toHaveBeenCalled()
-    expect((tools.log.error as any).mock.calls).toMatchSnapshot()
-    expect(tools.exit.failure).toHaveBeenCalled()
-  })
-})
+      .patch(/\/repos\/.*\/.*\/issues\/.*/)
+      .reply(500, {
+        message: "Updating issue failed",
+      });
+
+    await createAnIssue(tools);
+    expect(tools.exit.failure).toHaveBeenCalled();
+  });
+
+  it("logs a helpful error if creating an issue throws an error", async () => {
+    nock.cleanAll();
+    nock("https://api.github.com")
+      .get(/\/search\/issues.*/)
+      .reply(200, { items: [] })
+      .post(/\/repos\/.*\/.*\/issues/)
+      .reply(500, {
+        message: "Validation error",
+      });
+
+    await createAnIssue(tools);
+    expect(tools.log.error).toHaveBeenCalled();
+    expect((tools.log.error as any).mock.calls).toMatchSnapshot();
+    expect(tools.exit.failure).toHaveBeenCalled();
+  });
+
+  it("logs a helpful error if creating an issue throws an error with more errors", async () => {
+    nock.cleanAll();
+    nock("https://api.github.com")
+      .get(/\/search\/issues.*/)
+      .reply(200, { items: [] })
+      .post(/\/repos\/.*\/.*\/issues/)
+      .reply(500, {
+        message: "Validation error",
+        errors: [{ foo: true }],
+      });
+
+    await createAnIssue(tools);
+    expect(tools.log.error).toHaveBeenCalled();
+    expect((tools.log.error as any).mock.calls).toMatchSnapshot();
+    expect(tools.exit.failure).toHaveBeenCalled();
+  });
+
+  it("logs a helpful error if updating an issue throws an error with more errors", async () => {
+    nock.cleanAll();
+    nock("https://api.github.com")
+      .get(/\/search\/issues.*/)
+      .reply(200, { items: [{ number: 1, title: "Hello!" }] })
+      .patch(/\/repos\/.*\/.*\/issues\/.*/)
+      .reply(500, {
+        message: "Validation error",
+        errors: [{ foo: true }],
+      });
+
+    process.env.INPUT_UPDATE_EXISTING = "true";
+
+    await createAnIssue(tools);
+    expect(tools.log.error).toHaveBeenCalled();
+    expect((tools.log.error as any).mock.calls).toMatchSnapshot();
+    expect(tools.exit.failure).toHaveBeenCalled();
+  });
+
+  it("logs a helpful error if the frontmatter is invalid", async () => {
+    process.env.INPUT_FILENAME = ".github/invalid-frontmatter.md";
+
+    await createAnIssue(tools);
+    expect(tools.log.error).toHaveBeenCalled();
+    expect((tools.log.error as any).mock.calls).toMatchSnapshot();
+    expect(tools.exit.failure).toHaveBeenCalled();
+  });
+});
diff --git a/tests/setup.ts b/tests/setup.ts
index 88e73ba..ec76ca9 100644
--- a/tests/setup.ts
+++ b/tests/setup.ts
@@ -1,8 +1,8 @@
-const path = require('path')
+const path = require("path");
 
 Object.assign(process.env, {
-  GITHUB_REPOSITORY: 'JasonEtco/waddup',
-  GITHUB_ACTION: 'create-an-issue',
-  GITHUB_EVENT_PATH: path.join(__dirname, 'fixtures', 'event.json'),
-  GITHUB_WORKSPACE: path.join(__dirname, 'fixtures')
-})
+  GITHUB_REPOSITORY: "JasonEtco/waddup",
+  GITHUB_ACTION: "create-an-issue",
+  GITHUB_EVENT_PATH: path.join(__dirname, "fixtures", "event.json"),
+  GITHUB_WORKSPACE: path.join(__dirname, "fixtures"),
+});