diff --git a/.vscode/extensions.json b/.vscode/extensions.json
index e41e3004c..d795349ef 100644
--- a/.vscode/extensions.json
+++ b/.vscode/extensions.json
@@ -8,7 +8,8 @@
 		"streetsidesoftware.code-spell-checker",
 		"YoavBls.pretty-ts-errors",
 		"mxsdev.typescript-explorer",
-		"github.vscode-github-actions"
+		"github.vscode-github-actions",
+		"fabiospampinato.vscode-highlight"
 	],
 	// List of extensions recommended by VS Code that should not be recommended for users of this workspace.
 	"unwantedRecommendations": [
diff --git a/.vscode/settings.json b/.vscode/settings.json
index 92fc6a2ac..32205694b 100644
--- a/.vscode/settings.json
+++ b/.vscode/settings.json
@@ -103,5 +103,44 @@
     "**/start-server.js",
     "**/turbo/**"
   ],
-  "files.insertFinalNewline": true
+  "files.insertFinalNewline": true,
+  "highlight.regexes": {
+    "(import\\.meta\\.vitest\\?\\.test\\()[\"'`]([^\"'`]*)(.*)": [
+      {
+        "isWholeLine": true,
+        "before": {
+          "contentText": "test>  ",
+          "color": "#008080",
+          "fontStyle": "italic"
+        },
+      }
+    ],
+    "((?<=(?:import\\.meta\\.vitest\\?\\.test\\(.*\\n)(?:(?!(\\n\\}?\\);))[\\s\\S])*))\\n": [
+      {
+        "isWholeLine": true,
+        "before": {
+          "contentText": "       ",
+          "color": "#008080",
+          "fontStyle": "italic"
+        },
+      },
+    ],
+    "(import\\.meta\\.vitest\\?\\.test\\([\\s\\S]*?(\\n\\}?\\);))": [
+      {},
+      {
+        "isWholeLine": true,
+        "before": {
+          "contentText": "       ",
+          "color": "#008080",
+          "fontStyle": "italic"
+        },
+      },
+    ],
+
+    // disable the default TODO highlighting
+    "((?:<!-- *)?(?:#|// @|//|./\\*+|<!--|--|\\* @|{!|{{!--|{{!) *TODO(?:\\s*\\([^)]+\\))?:?)((?!\\w)(?: *-->| *\\*/| *!}| *--}}| *}}|(?= *(?:[^:]//|/\\*+|<!--|@|--|{!|{{!--|{{!))|(?: +[^\\n@]*?)(?= *(?:[^:]//|/\\*+|<!--|@|--(?!>)|{!|{{!--|{{!))|(?: +[^@\\n]+)?))": [],
+    "((?:<!-- *)?(?:#|// @|//|./\\*+|<!--|--|\\* @|{!|{{!--|{{!) *(?:FIXME|FIX|BUG|UGLY|DEBUG|HACK)(?:\\s*\\([^)]+\\))?:?)((?!\\w)(?: *-->| *\\*/| *!}| *--}}| *}}|(?= *(?:[^:]//|/\\*+|<!--|@|--|{!|{{!--|{{!))|(?: +[^\\n@]*?)(?= *(?:[^:]//|/\\*+|<!--|@|--(?!>)|{!|{{!--|{{!))|(?: +[^@\\n]+)?))": [],
+    "((?:<!-- *)?(?:#|// @|//|./\\*+|<!--|--|\\* @|{!|{{!--|{{!) *(?:REVIEW|OPTIMIZE|TSC)(?:\\s*\\([^)]+\\))?:?)((?!\\w)(?: *-->| *\\*/| *!}| *--}}| *}}|(?= *(?:[^:]//|/\\*+|<!--|@|--|{!|{{!--|{{!))|(?: +[^\\n@]*?)(?= *(?:[^:]//|/\\*+|<!--|@|--(?!>)|{!|{{!--|{{!))|(?: +[^@\\n]+)?))": [],
+    "((?:<!-- *)?(?:#|// @|//|./\\*+|<!--|--|\\* @|{!|{{!--|{{!) *(?:IDEA)(?:\\s*\\([^)]+\\))?:?)((?!\\w)(?: *-->| *\\*/| *!}| *--}}| *}}|(?= *(?:[^:]//|/\\*+|<!--|@|--|{!|{{!--|{{!))|(?: +[^\\n@]*?)(?= *(?:[^:]//|/\\*+|<!--|@|--(?!>)|{!|{{!--|{{!))|(?: +[^@\\n]+)?))": [],
+    }
 }
diff --git a/apps/backend/tsconfig.json b/apps/backend/tsconfig.json
index 2ee781786..5e9ab3978 100644
--- a/apps/backend/tsconfig.json
+++ b/apps/backend/tsconfig.json
@@ -27,7 +27,10 @@
         "./src/*"
       ]
     },
-    "skipLibCheck": true
+    "skipLibCheck": true,
+    "types": [
+      "vitest/importMeta"
+    ]
   },
   "include": [
     "next-env.d.ts",
diff --git a/apps/backend/vitest.config.ts b/apps/backend/vitest.config.ts
new file mode 100644
index 000000000..e4c46fede
--- /dev/null
+++ b/apps/backend/vitest.config.ts
@@ -0,0 +1,7 @@
+import { defineConfig, mergeConfig } from 'vitest/config'
+import sharedConfig from '../../vitest.shared'
+
+export default mergeConfig(
+  sharedConfig,
+  defineConfig({}),
+)
diff --git a/apps/dashboard/tsconfig.json b/apps/dashboard/tsconfig.json
index d39cb8dfc..956e00150 100644
--- a/apps/dashboard/tsconfig.json
+++ b/apps/dashboard/tsconfig.json
@@ -27,7 +27,10 @@
         "./src/*"
       ]
     },
-    "skipLibCheck": true
+    "skipLibCheck": true,
+    "types": [
+      "vitest/importMeta"
+    ]
   },
   "include": [
     "next-env.d.ts",
diff --git a/apps/dashboard/vitest.config.ts b/apps/dashboard/vitest.config.ts
new file mode 100644
index 000000000..e4c46fede
--- /dev/null
+++ b/apps/dashboard/vitest.config.ts
@@ -0,0 +1,7 @@
+import { defineConfig, mergeConfig } from 'vitest/config'
+import sharedConfig from '../../vitest.shared'
+
+export default mergeConfig(
+  sharedConfig,
+  defineConfig({}),
+)
diff --git a/apps/e2e/tsconfig.json b/apps/e2e/tsconfig.json
index 1f1a8f44d..64b3e3d6d 100644
--- a/apps/e2e/tsconfig.json
+++ b/apps/e2e/tsconfig.json
@@ -10,7 +10,10 @@
     "esModuleInterop": true,
     "noErrorTruncation": true,
     "strict": true,
-    "skipLibCheck": true
+    "skipLibCheck": true,
+    "types": [
+      "vitest/importMeta"
+    ]
   },
   "include": ["tests/**/*"],
   "exclude": ["node_modules", "dist"]
diff --git a/apps/e2e/vitest.config.ts b/apps/e2e/vitest.config.ts
index 7d3364c05..e3d5fe627 100644
--- a/apps/e2e/vitest.config.ts
+++ b/apps/e2e/vitest.config.ts
@@ -1,15 +1,19 @@
 import react from '@vitejs/plugin-react'
-import { defineConfig } from 'vitest/config'
+import { defineConfig, mergeConfig } from 'vitest/config'
+import sharedConfig from '../../vitest.shared'
 
-export default defineConfig({
-  plugins: [react()],
-  test: {
-    environment: 'node',
-    testTimeout: 20_000,
-    globalSetup: './tests/global-setup.ts',
-    setupFiles: [
-      "./tests/setup.ts",
-    ],
-    snapshotSerializers: ["./tests/snapshot-serializer.ts"],
-  },
-})
+export default mergeConfig(
+  sharedConfig,
+  defineConfig({
+    plugins: [react()],
+    test: {
+      environment: 'node',
+      testTimeout: 20_000,
+      globalSetup: './tests/global-setup.ts',
+      setupFiles: [
+        "./tests/setup.ts",
+      ],
+      snapshotSerializers: ["./tests/snapshot-serializer.ts"],
+    },
+  }),
+)
diff --git a/apps/oauth-mock-server/vitest.config.ts b/apps/oauth-mock-server/vitest.config.ts
new file mode 100644
index 000000000..e4c46fede
--- /dev/null
+++ b/apps/oauth-mock-server/vitest.config.ts
@@ -0,0 +1,7 @@
+import { defineConfig, mergeConfig } from 'vitest/config'
+import sharedConfig from '../../vitest.shared'
+
+export default mergeConfig(
+  sharedConfig,
+  defineConfig({}),
+)
diff --git a/package.json b/package.json
index dda4d8d9b..fb7e8cba9 100644
--- a/package.json
+++ b/package.json
@@ -39,6 +39,8 @@
     "peek": "pnpm pre && pnpm release --peek",
     "changeset": "pnpm pre && changeset",
     "test": "pnpm pre && vitest",
+    "test:e2e": "pnpm pre && vitest e2e/tests",
+    "test:unit": "pnpm pre && vitest src",
     "verify-data-integrity": "pnpm pre && pnpm -C apps/backend run verify-data-integrity",
     "generate-docs": "pnpm pre && turbo run generate-docs",
     "generate-keys": "pnpm pre && turbo run generate-keys",
diff --git a/packages/init-stack/vitest.config.ts b/packages/init-stack/vitest.config.ts
new file mode 100644
index 000000000..e4c46fede
--- /dev/null
+++ b/packages/init-stack/vitest.config.ts
@@ -0,0 +1,7 @@
+import { defineConfig, mergeConfig } from 'vitest/config'
+import sharedConfig from '../../vitest.shared'
+
+export default mergeConfig(
+  sharedConfig,
+  defineConfig({}),
+)
diff --git a/packages/stack-emails/tsconfig.json b/packages/stack-emails/tsconfig.json
index 35ed9fab9..fe75afb3c 100644
--- a/packages/stack-emails/tsconfig.json
+++ b/packages/stack-emails/tsconfig.json
@@ -11,7 +11,10 @@
     "esModuleInterop": true,
     "noErrorTruncation": true,
     "strict": true,
-    "skipLibCheck": true
+    "skipLibCheck": true,
+    "types": [
+      "vitest/importMeta"
+    ]
   },
   "include": ["src/**/*"],
   "exclude": ["node_modules", "dist"]
diff --git a/packages/stack-emails/vitest.config.ts b/packages/stack-emails/vitest.config.ts
new file mode 100644
index 000000000..e4c46fede
--- /dev/null
+++ b/packages/stack-emails/vitest.config.ts
@@ -0,0 +1,7 @@
+import { defineConfig, mergeConfig } from 'vitest/config'
+import sharedConfig from '../../vitest.shared'
+
+export default mergeConfig(
+  sharedConfig,
+  defineConfig({}),
+)
diff --git a/packages/stack-sc/tsconfig.json b/packages/stack-sc/tsconfig.json
index 75ddb0baf..67525231b 100644
--- a/packages/stack-sc/tsconfig.json
+++ b/packages/stack-sc/tsconfig.json
@@ -11,7 +11,10 @@
     "esModuleInterop": true,
     "noErrorTruncation": true,
     "skipLibCheck": true,
-    "strict": true
+    "strict": true,
+    "types": [
+      "vitest/importMeta"
+    ]
   },
   "include": ["src/**/*", "next-env.d.ts"],
   "exclude": ["node_modules", "dist"]
diff --git a/packages/stack-sc/vitest.config.ts b/packages/stack-sc/vitest.config.ts
new file mode 100644
index 000000000..e4c46fede
--- /dev/null
+++ b/packages/stack-sc/vitest.config.ts
@@ -0,0 +1,7 @@
+import { defineConfig, mergeConfig } from 'vitest/config'
+import sharedConfig from '../../vitest.shared'
+
+export default mergeConfig(
+  sharedConfig,
+  defineConfig({}),
+)
diff --git a/packages/stack-shared/package.json b/packages/stack-shared/package.json
index c6b16dcb8..6456ba751 100644
--- a/packages/stack-shared/package.json
+++ b/packages/stack-shared/package.json
@@ -7,6 +7,7 @@
   "scripts": {
     "build": "tsc",
     "typecheck": "tsc --noEmit",
+    "test": "vitest run",
     "clean": "rimraf dist && rimraf node_modules",
     "dev": "tsc -w --preserveWatchOutput --declarationMap",
     "lint": "eslint --ext .tsx,.ts ."
diff --git a/packages/stack-shared/src/utils/strings.test.ts b/packages/stack-shared/src/utils/strings.test.ts
new file mode 100644
index 000000000..307a672e3
--- /dev/null
+++ b/packages/stack-shared/src/utils/strings.test.ts
@@ -0,0 +1,33 @@
+import { describe, expect, it } from "vitest";
+import { templateIdentity } from "./strings";
+
+describe("templateIdentity", () => {
+  it("should be equivalent to a regular template string", () => {
+    const adjective = "scientific";
+    const noun = "railgun";
+    expect(templateIdentity`a certain scientific railgun`).toBe("a certain scientific railgun");
+    expect(templateIdentity`a certain ${adjective} railgun`).toBe(`a certain scientific railgun`);
+    expect(templateIdentity`a certain ${adjective} ${noun}`).toBe(`a certain scientific railgun`);
+    expect(templateIdentity`${adjective}${noun}`).toBe(`scientificrailgun`);
+  });
+
+  it("should work with empty strings", () => {
+    expect(templateIdentity``).toBe("");
+    expect(templateIdentity`${""}`).toBe("");
+    expect(templateIdentity`${""}${""}`).toBe("");
+  });
+
+  it("should work with normal arrays", () => {
+    expect(templateIdentity(
+      ["a ", " scientific ", "gun"],
+      "certain", "rail")
+    ).toBe("a certain scientific railgun");
+    expect(templateIdentity(["a"])).toBe("a");
+  });
+
+  it("should throw an error with wrong number of value arguments", () => {
+    expect(() => templateIdentity([])).toThrow();
+    expect(() => templateIdentity(["a", "b"])).toThrow();
+    expect(() => templateIdentity(["a", "b", "c"], "a", "b", "c")).toThrow();
+  });
+});
diff --git a/packages/stack-shared/src/utils/strings.tsx b/packages/stack-shared/src/utils/strings.tsx
index f2afe549d..5eb630b1e 100644
--- a/packages/stack-shared/src/utils/strings.tsx
+++ b/packages/stack-shared/src/utils/strings.tsx
@@ -70,6 +70,19 @@ export function trimEmptyLinesEnd(s: string): string {
 export function trimLines(s: string): string {
   return trimEmptyLinesEnd(trimEmptyLinesStart(s));
 }
+import.meta.vitest?.test("trimLines", ({ expect }) => {
+  expect(trimLines("")).toBe("");
+  expect(trimLines(" ")).toBe("");
+  expect(trimLines(" \n ")).toBe("");
+  expect(trimLines(" abc ")).toBe(" abc ");
+  expect(trimLines("\n  \nLine1\nLine2\n \n")).toBe("Line1\nLine2");
+  expect(trimLines("Line1\n   \nLine2")).toBe("Line1\n   \nLine2");
+  expect(trimLines(" \n    \n\t")).toBe("");
+  expect(trimLines("   Hello World")).toBe("   Hello World");
+  expect(trimLines("\n")).toBe("");
+  expect(trimLines("\t \n\t\tLine1 \n \nLine2\t\t\n\t  ")).toBe("\t\tLine1 \n \nLine2\t\t");
+});
+
 
 /**
  * A template literal tag that returns the same string as the template literal without a tag.
@@ -77,8 +90,26 @@ export function trimLines(s: string): string {
  * Useful for implementing your own template literal tags.
  */
 export function templateIdentity(strings: TemplateStringsArray | readonly string[], ...values: string[]): string {
+  if (values.length !== strings.length - 1) throw new StackAssertionError("Invalid number of values; must be one less than strings", { strings, values });
+
   return strings.reduce((result, str, i) => result + str + (values[i] ?? ''), '');
 }
+import.meta.vitest?.test("templateIdentity", ({ expect }) => {
+  expect(templateIdentity`Hello World`).toBe("Hello World");
+  expect(templateIdentity`${"Hello"}`).toBe("Hello");
+  const greeting = "Hello";
+  const subject = "World";
+  expect(templateIdentity`${greeting}, ${subject}!`).toBe("Hello, World!");
+  expect(templateIdentity`${"A"}${"B"}${"C"}`).toBe("ABC");
+  expect(templateIdentity`Start${""}Middle${""}End`).toBe("StartMiddleEnd");
+  expect(templateIdentity``).toBe("");
+  expect(templateIdentity`Line1
+Line2`).toBe("Line1\nLine2");
+  expect(templateIdentity(["a ", " scientific ", "gun"], "certain", "rail")).toBe("a certain scientific railgun");
+  expect(templateIdentity(["only one part"])).toBe("only one part");
+  expect(() => templateIdentity(["a ", "b", "c"], "only one")).toThrow("Invalid number of values");
+  expect(() => templateIdentity(["a", "b"], "x", "y")).toThrow("Invalid number of values");
+});
 
 
 export function deindent(code: string): string;
@@ -86,7 +117,7 @@ export function deindent(strings: TemplateStringsArray | readonly string[], ...v
 export function deindent(strings: string | readonly string[], ...values: any[]): string {
   if (typeof strings === "string") return deindent([strings]);
   if (strings.length === 0) return "";
-  if (values.length !== strings.length - 1) throw new Error("Invalid number of values; must be one less than strings");
+  if (values.length !== strings.length - 1) throw new StackAssertionError("Invalid number of values; must be one less than strings", { strings, values });
 
   const trimmedStrings = [...strings];
   trimmedStrings[0] = trimEmptyLinesStart(trimmedStrings[0]);
diff --git a/packages/stack-shared/tsconfig.json b/packages/stack-shared/tsconfig.json
index 35ed9fab9..6a98bd1ab 100644
--- a/packages/stack-shared/tsconfig.json
+++ b/packages/stack-shared/tsconfig.json
@@ -6,12 +6,15 @@
     "declaration": true,
     "target": "ES2021",
     "lib": ["DOM", "DOM.Iterable", "ES2021", "ES2022.Error"],
-    "module": "ES2015",
+    "module": "ES2020",
     "moduleResolution": "Bundler",
     "esModuleInterop": true,
     "noErrorTruncation": true,
     "strict": true,
-    "skipLibCheck": true
+    "skipLibCheck": true,
+    "types": [
+      "vitest/importMeta"
+    ]
   },
   "include": ["src/**/*"],
   "exclude": ["node_modules", "dist"]
diff --git a/packages/stack-shared/vitest.config.ts b/packages/stack-shared/vitest.config.ts
new file mode 100644
index 000000000..e4c46fede
--- /dev/null
+++ b/packages/stack-shared/vitest.config.ts
@@ -0,0 +1,7 @@
+import { defineConfig, mergeConfig } from 'vitest/config'
+import sharedConfig from '../../vitest.shared'
+
+export default mergeConfig(
+  sharedConfig,
+  defineConfig({}),
+)
diff --git a/packages/stack-ui/tsconfig.json b/packages/stack-ui/tsconfig.json
index 54d81fc8d..6a98bd1ab 100644
--- a/packages/stack-ui/tsconfig.json
+++ b/packages/stack-ui/tsconfig.json
@@ -11,7 +11,10 @@
     "esModuleInterop": true,
     "noErrorTruncation": true,
     "strict": true,
-    "skipLibCheck": true
+    "skipLibCheck": true,
+    "types": [
+      "vitest/importMeta"
+    ]
   },
   "include": ["src/**/*"],
   "exclude": ["node_modules", "dist"]
diff --git a/packages/stack-ui/vitest.config.ts b/packages/stack-ui/vitest.config.ts
new file mode 100644
index 000000000..e4c46fede
--- /dev/null
+++ b/packages/stack-ui/vitest.config.ts
@@ -0,0 +1,7 @@
+import { defineConfig, mergeConfig } from 'vitest/config'
+import sharedConfig from '../../vitest.shared'
+
+export default mergeConfig(
+  sharedConfig,
+  defineConfig({}),
+)
diff --git a/packages/template/tsconfig.json b/packages/template/tsconfig.json
index f91a58ebc..c9d710bd7 100644
--- a/packages/template/tsconfig.json
+++ b/packages/template/tsconfig.json
@@ -13,7 +13,10 @@
     "skipLibCheck": true,
     "strict": true,
     "sourceMap": true,
-    "declarationMap": true
+    "declarationMap": true,
+    "types": [
+      "vitest/importMeta"
+    ]
   },
   "include": ["next-env.d.ts", "src/**/*", ".next/types/**/*.ts"],
   "exclude": ["node_modules", "dist"]
diff --git a/packages/template/vitest.config.ts b/packages/template/vitest.config.ts
new file mode 100644
index 000000000..e4c46fede
--- /dev/null
+++ b/packages/template/vitest.config.ts
@@ -0,0 +1,7 @@
+import { defineConfig, mergeConfig } from 'vitest/config'
+import sharedConfig from '../../vitest.shared'
+
+export default mergeConfig(
+  sharedConfig,
+  defineConfig({}),
+)
diff --git a/vitest.shared.ts b/vitest.shared.ts
new file mode 100644
index 000000000..3345d4575
--- /dev/null
+++ b/vitest.shared.ts
@@ -0,0 +1,8 @@
+import { defineConfig } from 'vitest/config'
+
+export default defineConfig({
+  test: {
+    include: ['**/*.test.{js,ts,jsx,tsx}'],
+    includeSource: ['**/*.{js,ts,jsx,tsx}'], 
+  },
+})
diff --git a/vitest.workspace.ts b/vitest.workspace.ts
index f7f05ed78..086847324 100644
--- a/vitest.workspace.ts
+++ b/vitest.workspace.ts
@@ -1,6 +1,8 @@
-export default [
+import { defineWorkspace } from 'vitest/config';
+
+export default defineWorkspace([
   'packages/*',
   'apps/*',
   'examples/*',
   'docs',
-];
+]);