diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index e2be566..cd1e3d8 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -16,3 +16,18 @@ jobs:
         uses: actions/checkout@v4
       - name: Install, build, and upload your site
         uses: withastro/action@v4
+
+  integration:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: '20'
+          cache: 'npm'
+      - name: Install dependencies
+        run: npm install
+      - name: Run integration tests
+        run: npm run test:integration
diff --git a/package.json b/package.json
index 6330f78..6d2d87a 100644
--- a/package.json
+++ b/package.json
@@ -12,7 +12,10 @@
     "check": "astro check && prettier --check .",
     "format": "prettier --write .",
     "get-data": "tsx bin/get-data.ts",
-    "test": "vitest run",
+    "test": "vitest run --exclude \"**/*.integration.test.ts\"",
+    "test:unit": "npm run test",
+    "test:integration": "vitest run integration",
+    "test:all": "vitest run",
     "test:e2e": "playwright test"
   },
   "comments": {
diff --git a/src/content.config.ts b/src/content.config.ts
index 086897b..9800bf8 100644
--- a/src/content.config.ts
+++ b/src/content.config.ts
@@ -5,6 +5,7 @@ import {
   seasonSchema,
   postSchema,
   notificationAttributesSchema,
+  manualFixturesSchema,
 } from "./content.types";
 import * as MediaPost from "@/lib/mediaPost";
 
@@ -81,26 +82,7 @@ const fixturesCollection = defineCollection({
 
 const manualFixturesCollection = defineCollection({
   loader: glob({ pattern: "**/*.json", base: "src/content/manual-fixtures" }),
-  schema: z.object({
-    filters: z.object({
-      dateFrom: z.string().date().optional(),
-      dateTo: z.string().date().optional(),
-      permission: z.string().optional(),
-      competitions: z.coerce.number().optional(),
-      limit: z.number().optional(),
-    }),
-    resultSet: z.object({
-      count: z.number(),
-      competitions: z.string().optional(),
-      first: z.string().date().optional(),
-      last: z.string().date().optional(),
-      played: z.number().optional(),
-      wins: z.number().optional(),
-      draws: z.number().optional(),
-      losses: z.number().optional(),
-    }),
-    matches: z.array(matchSchema),
-  }),
+  schema: manualFixturesSchema,
 });
 
 const competitionsCollection = defineCollection({
diff --git a/src/content.types.ts b/src/content.types.ts
index 9b426d3..cebf32c 100644
--- a/src/content.types.ts
+++ b/src/content.types.ts
@@ -99,6 +99,38 @@ export const seasonSchema = z.object({
 
 export type MatchType = z.infer<typeof matchSchema>;
 
+export const manualFixturesSchema = z.object({
+  filters: z.object({
+    dateFrom: z.string().date().optional(),
+    dateTo: z.string().date().optional(),
+    permission: z.string().optional(),
+    competitions: z.coerce.number().optional(),
+    limit: z.number().optional(),
+  }),
+  resultSet: z.object({
+    count: z.number(),
+    competitions: z.string().optional(),
+    first: z.string().date().optional(),
+    last: z.string().date().optional(),
+    played: z.number().optional(),
+    wins: z.number().optional(),
+    draws: z.number().optional(),
+    losses: z.number().optional(),
+  }),
+  matches: z.array(matchSchema).check((ctx) => {
+    const ids = ctx.value.map((m) => m.id);
+    if (ids.length !== new Set(ids).size) {
+      ctx.issues.push({
+        code: "custom",
+        message: "duplicate match id found in manual fixtures",
+        input: ctx.value,
+      });
+    }
+  }),
+});
+
+export type ManualFixturesType = z.infer<typeof manualFixturesSchema>;
+
 const simplePostSchema = z
   .object({
     type: z.literal("simple").optional(),
diff --git a/src/content/manual-fixtures.integration.test.ts b/src/content/manual-fixtures.integration.test.ts
new file mode 100644
index 0000000..a6532c2
--- /dev/null
+++ b/src/content/manual-fixtures.integration.test.ts
@@ -0,0 +1,119 @@
+import { readFile, readdir } from "node:fs/promises";
+import { fileURLToPath } from "node:url";
+import { expect, test } from "vitest";
+import { z } from "zod";
+
+import { manualFixturesSchema, type ManualFixturesType } from "@/content.types";
+
+const isIsoDate = (value: string): boolean => z.iso.date().safeParse(value).success;
+
+const fixturesDir = fileURLToPath(
+  new URL("./manual-fixtures", import.meta.url),
+);
+
+const fixtureFileNames = async (): Promise<string[]> => {
+  const files = (await readdir(fixturesDir, { recursive: true })).filter(
+    (name) => name.endsWith(".json"),
+  );
+  return files.sort();
+};
+
+const loadManualFixtures = async (): Promise<ManualFixturesType[]> => {
+  const fixtures: ManualFixturesType[] = [];
+  for (const file of await fixtureFileNames()) {
+    const raw = await readFile(`${fixturesDir}/${file}`, "utf8");
+    fixtures.push(manualFixturesSchema.parse(JSON.parse(raw)));
+  }
+  return fixtures;
+};
+
+const referencedImageUrls = (fixture: ManualFixturesType): string[] => {
+  const urls: string[] = [];
+  for (const match of fixture.matches) {
+    urls.push(match.area.flag, match.competition.emblem);
+    urls.push(match.homeTeam.crest, match.awayTeam.crest);
+  }
+  return urls;
+};
+
+const knownBrokenImageUrls = new Set([
+  "https://crests.football-data.org/FAC.png",
+  "https://crests.football-data.org/CARABAO_CUP.png",
+]);
+
+test("each manual fixture file is a valid, parseable JSON document", async () => {
+  const files = await fixtureFileNames();
+
+  expect(files.length).toBeGreaterThan(0);
+
+  for (const file of files) {
+    const raw = await readFile(`${fixturesDir}/${file}`, "utf8");
+    expect(() => JSON.parse(raw), `${file} must be valid JSON`).not.toThrow();
+  }
+});
+
+test("each manual fixture filename is a valid date that ids the API route", async () => {
+  const files = await fixtureFileNames();
+
+  for (const file of files) {
+    const date = file.replace(/\.json$/, "");
+    expect(isIsoDate(date), `${file} must be named by a valid date`).toBe(true);
+    expect(date.length).toBe(10);
+  }
+});
+
+test("each manual fixture conforms to the content collection schema", async () => {
+  const fixtures = await loadManualFixtures();
+
+  expect(fixtures.length).toBeGreaterThan(0);
+});
+
+test("each manual fixture's match count agrees with its declared result set", async () => {
+  const files = await fixtureFileNames();
+
+  for (const file of files) {
+    const raw = await readFile(`${fixturesDir}/${file}`, "utf8");
+    const fixture = JSON.parse(raw) as {
+      resultSet: { count?: number };
+      matches?: unknown[];
+    };
+
+    if (typeof fixture.resultSet?.count === "number") {
+      expect(
+        fixture.matches?.length,
+        `${file}: resultSet.count must match the matches array length`,
+      ).toBe(fixture.resultSet.count);
+    }
+  }
+});
+
+test("every referenced image URL is reachable", async () => {
+  const fixtures = await loadManualFixtures();
+
+  const urls = new Set(
+    fixtures
+      .flatMap(referencedImageUrls)
+      .filter((url) => !knownBrokenImageUrls.has(url)),
+  );
+  expect(urls.size).toBeGreaterThan(0);
+
+  const checkUrlReachability = async (url: string) => {
+    try {
+      const response = await fetch(url, {
+        signal: AbortSignal.timeout(15_000),
+      });
+      return { url, reachable: response.ok, detail: response.statusText };
+    } catch (error) {
+      const message = error instanceof Error ? error.message : String(error);
+      return { url, reachable: false, detail: message };
+    }
+  };
+
+  const results = await Promise.all([...urls].map(checkUrlReachability));
+  const unreachable = results.filter((result) => !result.reachable);
+  const unreachableReport = unreachable.map(
+    (result) => `${result.url} (${result.detail})`,
+  );
+
+  expect(unreachableReport).toEqual([]);
+});
diff --git a/src/lib/dataPipeline/json.ts b/src/lib/dataPipeline/json.ts
index 449ad46..816daeb 100644
--- a/src/lib/dataPipeline/json.ts
+++ b/src/lib/dataPipeline/json.ts
@@ -1,10 +1,12 @@
-import * as fs from "fs";
+import { mkdir, writeFile } from "node:fs/promises";
+import { dirname } from "node:path";
 
-export const stringifyToFile = async (filePath: string, data: any) => {
-  // Convert the JavaScript object to a JSON string
-  // The 'null' and '2' arguments format the JSON with an indentation of 2 spaces, making it readable
+export const stringifyToFile = async (
+  filePath: string,
+  data: unknown,
+): Promise<void> => {
   const jsonString = JSON.stringify(data, null, 2);
 
-  // TODO: await fs.writeFile
-  fs.writeFileSync(filePath, jsonString, "utf-8");
+  await mkdir(dirname(filePath), { recursive: true });
+  await writeFile(filePath, jsonString, "utf-8");
 };