diff --git a/__tests__/labeler.test.ts b/__tests__/labeler.test.ts
new file mode 100644
index 0000000..d7195cd
--- /dev/null
+++ b/__tests__/labeler.test.ts
@@ -0,0 +1,29 @@
+import { checkGlobs } from '../src/labeler'
+
+import * as core from "@actions/core";
+
+jest.mock("@actions/core");
+
+beforeAll(() => {
+  jest.spyOn(core, "getInput").mockImplementation((name, options) => {
+    return jest.requireActual("@actions/core").getInput(name, options);
+  });
+});
+
+const matchConfig = [{ any: ["*.txt"] }];
+
+describe('checkGlobs', () => {
+  it('returns true when our pattern does match changed files', () => {
+    const changedFiles = ["foo.txt", "bar.txt"];
+    const result = checkGlobs(changedFiles, matchConfig);
+
+    expect(result).toBeTruthy();
+  });
+
+  it('returns false when our pattern does not match changed files', () => {
+    const changedFiles = ["foo.docx"];
+    const result = checkGlobs(changedFiles, matchConfig);
+
+    expect(result).toBeFalsy();
+  });
+});
diff --git a/__tests__/main.test.ts b/__tests__/main.test.ts
deleted file mode 100644
index 42af5f1..0000000
--- a/__tests__/main.test.ts
+++ /dev/null
@@ -1,3 +0,0 @@
-describe("TODO - Add a test suite", () => {
-  it("TODO - Add a test", async () => {});
-});
diff --git a/src/labeler.ts b/src/labeler.ts
new file mode 100644
index 0000000..f7054a4
--- /dev/null
+++ b/src/labeler.ts
@@ -0,0 +1,259 @@
+import * as core from "@actions/core";
+import * as github from "@actions/github";
+import * as yaml from "js-yaml";
+import { Minimatch, IMinimatch } from "minimatch";
+
+interface MatchConfig {
+  all?: string[];
+  any?: string[];
+}
+
+type StringOrMatchConfig = string | MatchConfig;
+
+export async function run() {
+  try {
+    const token = core.getInput("repo-token", { required: true });
+    const configPath = core.getInput("configuration-path", { required: true });
+    const syncLabels = !!core.getInput("sync-labels", { required: false });
+
+    const prNumber = getPrNumber();
+    if (!prNumber) {
+      console.log("Could not get pull request number from context, exiting");
+      return;
+    }
+
+    const client = new github.GitHub(token);
+
+    const { data: pullRequest } = await client.pulls.get({
+      owner: github.context.repo.owner,
+      repo: github.context.repo.repo,
+      pull_number: prNumber
+    });
+
+    core.debug(`fetching changed files for pr #${prNumber}`);
+    const changedFiles: string[] = await getChangedFiles(client, prNumber);
+    const labelGlobs: Map<string, StringOrMatchConfig[]> = await getLabelGlobs(
+      client,
+      configPath
+    );
+
+    const labels: string[] = [];
+    const labelsToRemove: string[] = [];
+    for (const [label, globs] of labelGlobs.entries()) {
+      core.debug(`processing ${label}`);
+      if (checkGlobs(changedFiles, globs)) {
+        labels.push(label);
+      } else if (pullRequest.labels.find(l => l.name === label)) {
+        labelsToRemove.push(label);
+      }
+    }
+
+    if (labels.length > 0) {
+      await addLabels(client, prNumber, labels);
+    }
+
+    if (syncLabels && labelsToRemove.length) {
+      await removeLabels(client, prNumber, labelsToRemove);
+    }
+  } catch (error) {
+    core.error(error);
+    core.setFailed(error.message);
+  }
+}
+
+function getPrNumber(): number | undefined {
+  const pullRequest = github.context.payload.pull_request;
+  if (!pullRequest) {
+    return undefined;
+  }
+
+  return pullRequest.number;
+}
+
+async function getChangedFiles(
+  client: github.GitHub,
+  prNumber: number
+): Promise<string[]> {
+  const listFilesOptions = client.pulls.listFiles.endpoint.merge({
+    owner: github.context.repo.owner,
+    repo: github.context.repo.repo,
+    pull_number: prNumber
+  });
+
+  const listFilesResponse = await client.paginate(listFilesOptions);
+  const changedFiles = listFilesResponse.map(f => f.filename);
+
+  core.debug("found changed files:");
+  for (const file of changedFiles) {
+    core.debug("  " + file);
+  }
+
+  return changedFiles;
+}
+
+async function getLabelGlobs(
+  client: github.GitHub,
+  configurationPath: string
+): Promise<Map<string, StringOrMatchConfig[]>> {
+  const configurationContent: string = await fetchContent(
+    client,
+    configurationPath
+  );
+
+  // loads (hopefully) a `{[label:string]: string | StringOrMatchConfig[]}`, but is `any`:
+  const configObject: any = yaml.safeLoad(configurationContent);
+
+  // transform `any` => `Map<string,StringOrMatchConfig[]>` or throw if yaml is malformed:
+  return getLabelGlobMapFromObject(configObject);
+}
+
+async function fetchContent(
+  client: github.GitHub,
+  repoPath: string
+): Promise<string> {
+  const response: any = await client.repos.getContents({
+    owner: github.context.repo.owner,
+    repo: github.context.repo.repo,
+    path: repoPath,
+    ref: github.context.sha
+  });
+
+  return Buffer.from(response.data.content, response.data.encoding).toString();
+}
+
+function getLabelGlobMapFromObject(
+  configObject: any
+): Map<string, StringOrMatchConfig[]> {
+  const labelGlobs: Map<string, StringOrMatchConfig[]> = new Map();
+  for (const label in configObject) {
+    if (typeof configObject[label] === "string") {
+      labelGlobs.set(label, [configObject[label]]);
+    } else if (configObject[label] instanceof Array) {
+      labelGlobs.set(label, configObject[label]);
+    } else {
+      throw Error(
+        `found unexpected type for label ${label} (should be string or array of globs)`
+      );
+    }
+  }
+
+  return labelGlobs;
+}
+
+function toMatchConfig(config: StringOrMatchConfig): MatchConfig {
+  if (typeof config === "string") {
+    return {
+      any: [config]
+    };
+  }
+
+  return config;
+}
+
+function printPattern(matcher: IMinimatch): string {
+  return (matcher.negate ? "!" : "") + matcher.pattern;
+}
+
+export function checkGlobs(
+  changedFiles: string[],
+  globs: StringOrMatchConfig[]
+): boolean {
+  for (const glob of globs) {
+    core.debug(` checking pattern ${JSON.stringify(glob)}`);
+    const matchConfig = toMatchConfig(glob);
+    if (checkMatch(changedFiles, matchConfig)) {
+      return true;
+    }
+  }
+  return false;
+}
+
+function isMatch(changedFile: string, matchers: IMinimatch[]): boolean {
+  core.debug(`    matching patterns against file ${changedFile}`);
+  for (const matcher of matchers) {
+    core.debug(`   - ${printPattern(matcher)}`);
+    if (!matcher.match(changedFile)) {
+      core.debug(`   ${printPattern(matcher)} did not match`);
+      return false;
+    }
+  }
+
+  core.debug(`   all patterns matched`);
+  return true;
+}
+
+// equivalent to "Array.some()" but expanded for debugging and clarity
+function checkAny(changedFiles: string[], globs: string[]): boolean {
+  const matchers = globs.map(g => new Minimatch(g));
+  core.debug(`  checking "any" patterns`);
+  for (const changedFile of changedFiles) {
+    if (isMatch(changedFile, matchers)) {
+      core.debug(`  "any" patterns matched against ${changedFile}`);
+      return true;
+    }
+  }
+
+  core.debug(`  "any" patterns did not match any files`);
+  return false;
+}
+
+// equivalent to "Array.every()" but expanded for debugging and clarity
+function checkAll(changedFiles: string[], globs: string[]): boolean {
+  const matchers = globs.map(g => new Minimatch(g));
+  core.debug(` checking "all" patterns`);
+  for (const changedFile of changedFiles) {
+    if (!isMatch(changedFile, matchers)) {
+      core.debug(`  "all" patterns did not match against ${changedFile}`);
+      return false;
+    }
+  }
+
+  core.debug(`  "all" patterns matched all files`);
+  return true;
+}
+
+function checkMatch(changedFiles: string[], matchConfig: MatchConfig): boolean {
+  if (matchConfig.all !== undefined) {
+    if (!checkAll(changedFiles, matchConfig.all)) {
+      return false;
+    }
+  }
+
+  if (matchConfig.any !== undefined) {
+    if (!checkAny(changedFiles, matchConfig.any)) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+async function addLabels(
+  client: github.GitHub,
+  prNumber: number,
+  labels: string[]
+) {
+  await client.issues.addLabels({
+    owner: github.context.repo.owner,
+    repo: github.context.repo.repo,
+    issue_number: prNumber,
+    labels: labels
+  });
+}
+
+async function removeLabels(
+  client: github.GitHub,
+  prNumber: number,
+  labels: string[]
+) {
+  await Promise.all(
+    labels.map(label =>
+      client.issues.removeLabel({
+        owner: github.context.repo.owner,
+        repo: github.context.repo.repo,
+        issue_number: prNumber,
+        name: label
+      })
+    )
+  );
+}
diff --git a/src/main.ts b/src/main.ts
index 971fd99..d9d6212 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -1,261 +1,3 @@
-import * as core from "@actions/core";
-import * as github from "@actions/github";
-import * as yaml from "js-yaml";
-import { Minimatch, IMinimatch } from "minimatch";
-
-interface MatchConfig {
-  all?: string[];
-  any?: string[];
-}
-
-type StringOrMatchConfig = string | MatchConfig;
-
-async function run() {
-  try {
-    const token = core.getInput("repo-token", { required: true });
-    const configPath = core.getInput("configuration-path", { required: true });
-    const syncLabels = !!core.getInput("sync-labels", { required: false });
-
-    const prNumber = getPrNumber();
-    if (!prNumber) {
-      console.log("Could not get pull request number from context, exiting");
-      return;
-    }
-
-    const client = new github.GitHub(token);
-
-    const { data: pullRequest } = await client.pulls.get({
-      owner: github.context.repo.owner,
-      repo: github.context.repo.repo,
-      pull_number: prNumber
-    });
-
-    core.debug(`fetching changed files for pr #${prNumber}`);
-    const changedFiles: string[] = await getChangedFiles(client, prNumber);
-    const labelGlobs: Map<string, StringOrMatchConfig[]> = await getLabelGlobs(
-      client,
-      configPath
-    );
-
-    const labels: string[] = [];
-    const labelsToRemove: string[] = [];
-    for (const [label, globs] of labelGlobs.entries()) {
-      core.debug(`processing ${label}`);
-      if (checkGlobs(changedFiles, globs)) {
-        labels.push(label);
-      } else if (pullRequest.labels.find(l => l.name === label)) {
-        labelsToRemove.push(label);
-      }
-    }
-
-    if (labels.length > 0) {
-      await addLabels(client, prNumber, labels);
-    }
-
-    if (syncLabels && labelsToRemove.length) {
-      await removeLabels(client, prNumber, labelsToRemove);
-    }
-  } catch (error) {
-    core.error(error);
-    core.setFailed(error.message);
-  }
-}
-
-function getPrNumber(): number | undefined {
-  const pullRequest = github.context.payload.pull_request;
-  if (!pullRequest) {
-    return undefined;
-  }
-
-  return pullRequest.number;
-}
-
-async function getChangedFiles(
-  client: github.GitHub,
-  prNumber: number
-): Promise<string[]> {
-  const listFilesOptions = client.pulls.listFiles.endpoint.merge({
-    owner: github.context.repo.owner,
-    repo: github.context.repo.repo,
-    pull_number: prNumber
-  });
-
-  const listFilesResponse = await client.paginate(listFilesOptions);
-  const changedFiles = listFilesResponse.map(f => f.filename);
-
-  core.debug("found changed files:");
-  for (const file of changedFiles) {
-    core.debug("  " + file);
-  }
-
-  return changedFiles;
-}
-
-async function getLabelGlobs(
-  client: github.GitHub,
-  configurationPath: string
-): Promise<Map<string, StringOrMatchConfig[]>> {
-  const configurationContent: string = await fetchContent(
-    client,
-    configurationPath
-  );
-
-  // loads (hopefully) a `{[label:string]: string | StringOrMatchConfig[]}`, but is `any`:
-  const configObject: any = yaml.safeLoad(configurationContent);
-
-  // transform `any` => `Map<string,StringOrMatchConfig[]>` or throw if yaml is malformed:
-  return getLabelGlobMapFromObject(configObject);
-}
-
-async function fetchContent(
-  client: github.GitHub,
-  repoPath: string
-): Promise<string> {
-  const response: any = await client.repos.getContents({
-    owner: github.context.repo.owner,
-    repo: github.context.repo.repo,
-    path: repoPath,
-    ref: github.context.sha
-  });
-
-  return Buffer.from(response.data.content, response.data.encoding).toString();
-}
-
-function getLabelGlobMapFromObject(
-  configObject: any
-): Map<string, StringOrMatchConfig[]> {
-  const labelGlobs: Map<string, StringOrMatchConfig[]> = new Map();
-  for (const label in configObject) {
-    if (typeof configObject[label] === "string") {
-      labelGlobs.set(label, [configObject[label]]);
-    } else if (configObject[label] instanceof Array) {
-      labelGlobs.set(label, configObject[label]);
-    } else {
-      throw Error(
-        `found unexpected type for label ${label} (should be string or array of globs)`
-      );
-    }
-  }
-
-  return labelGlobs;
-}
-
-function toMatchConfig(config: StringOrMatchConfig): MatchConfig {
-  if (typeof config === "string") {
-    return {
-      any: [config]
-    };
-  }
-
-  return config;
-}
-
-function printPattern(matcher: IMinimatch): string {
-  return (matcher.negate ? "!" : "") + matcher.pattern;
-}
-
-function checkGlobs(
-  changedFiles: string[],
-  globs: StringOrMatchConfig[]
-): boolean {
-  for (const glob of globs) {
-    core.debug(` checking pattern ${JSON.stringify(glob)}`);
-    const matchConfig = toMatchConfig(glob);
-    if (checkMatch(changedFiles, matchConfig)) {
-      return true;
-    }
-  }
-  return false;
-}
-
-function isMatch(changedFile: string, matchers: IMinimatch[]): boolean {
-  core.debug(`    matching patterns against file ${changedFile}`);
-  for (const matcher of matchers) {
-    core.debug(`   - ${printPattern(matcher)}`);
-    if (!matcher.match(changedFile)) {
-      core.debug(`   ${printPattern(matcher)} did not match`);
-      return false;
-    }
-  }
-
-  core.debug(`   all patterns matched`);
-  return true;
-}
-
-// equivalent to "Array.some()" but expanded for debugging and clarity
-function checkAny(changedFiles: string[], globs: string[]): boolean {
-  const matchers = globs.map(g => new Minimatch(g));
-  core.debug(`  checking "any" patterns`);
-  for (const changedFile of changedFiles) {
-    if (isMatch(changedFile, matchers)) {
-      core.debug(`  "any" patterns matched against ${changedFile}`);
-      return true;
-    }
-  }
-
-  core.debug(`  "any" patterns did not match any files`);
-  return false;
-}
-
-// equivalent to "Array.every()" but expanded for debugging and clarity
-function checkAll(changedFiles: string[], globs: string[]): boolean {
-  const matchers = globs.map(g => new Minimatch(g));
-  core.debug(` checking "all" patterns`);
-  for (const changedFile of changedFiles) {
-    if (!isMatch(changedFile, matchers)) {
-      core.debug(`  "all" patterns did not match against ${changedFile}`);
-      return false;
-    }
-  }
-
-  core.debug(`  "all" patterns matched all files`);
-  return true;
-}
-
-function checkMatch(changedFiles: string[], matchConfig: MatchConfig): boolean {
-  if (matchConfig.all !== undefined) {
-    if (!checkAll(changedFiles, matchConfig.all)) {
-      return false;
-    }
-  }
-
-  if (matchConfig.any !== undefined) {
-    if (!checkAny(changedFiles, matchConfig.any)) {
-      return false;
-    }
-  }
-
-  return true;
-}
-
-async function addLabels(
-  client: github.GitHub,
-  prNumber: number,
-  labels: string[]
-) {
-  await client.issues.addLabels({
-    owner: github.context.repo.owner,
-    repo: github.context.repo.repo,
-    issue_number: prNumber,
-    labels: labels
-  });
-}
-
-async function removeLabels(
-  client: github.GitHub,
-  prNumber: number,
-  labels: string[]
-) {
-  await Promise.all(
-    labels.map(label =>
-      client.issues.removeLabel({
-        owner: github.context.repo.owner,
-        repo: github.context.repo.repo,
-        issue_number: prNumber,
-        name: label
-      })
-    )
-  );
-}
+import { run } from "./labeler";
 
 run();