diff --git a/README.md b/README.md
index 3d385ef..d480a35 100644
--- a/README.md
+++ b/README.md
@@ -198,7 +198,7 @@ func Main() -> int {
 | **CTFE** | `const func` — compile-time function execution |
 | **Trait Bounds** | `func Max<T: Comparable>(a: T, b: T) -> T` |
 | **Package Manager** | `bux add`, `bux install`, `bux.lock`, path + git deps |
-| **Tooling** | `bux new`, `bux build`, `bux run`, `bux check` |
+| **Tooling** | `bux new`, `bux build`, `bux run`, `bux test`, `bux check` |
 
 ---
 
diff --git a/compiler/bootstrap/cli.nim b/compiler/bootstrap/cli.nim
index 80a9809..de17d77 100644
--- a/compiler/bootstrap/cli.nim
+++ b/compiler/bootstrap/cli.nim
@@ -24,6 +24,7 @@ Commands:
   install             Resolve and install dependencies
   build               Build the current package
   run                 Build and run the current package
+  test                Run tests in tests/ directory
   check               Type-check the current package
   clean               Remove build artifacts
   help                Show this help message
@@ -574,6 +575,46 @@ proc cmdClean*(args: seq[string], opts: GlobalOptions): int =
     printInfo("clean: build directory removed", useColor)
   return 0
 
+proc cmdTest*(args: seq[string], opts: GlobalOptions): int =
+  let useColor = shouldUseColor(opts)
+  let root = getCurrentDir()
+  let testsDir = root / "tests"
+  var testFiles: seq[string] = @[]
+  if dirExists(testsDir):
+    for kind, path in walkDir(testsDir):
+      if kind == pcFile and path.endsWith(".bux"):
+        testFiles.add(path)
+  if testFiles.len == 0:
+    printError("no tests found in tests/ directory", useColor)
+    return 1
+  var passed = 0
+  var failed = 0
+  for testFile in testFiles:
+    let testName = splitFile(testFile).name
+    let tmpDir = getTempDir() / "bux_test_" & testName
+    removeDir(tmpDir)
+    createDir(tmpDir / "src")
+    copyFile(testFile, tmpDir / "src" / "Main.bux")
+    writeFile(tmpDir / "bux.toml", "[package]\nname = \"" & testName & "\"\nversion = \"0.1.0\"\n")
+    let buildRes = cmdBuild(@[tmpDir], opts)
+    if buildRes != 0:
+      printError(&"  FAIL {testName} (build)", useColor)
+      failed += 1
+      continue
+    var execFile = tmpDir / "build" / testName
+    if not fileExists(execFile):
+      execFile = tmpDir / "build" / "bux_out"
+    let exitCode = execCmd(execFile)
+    if exitCode == 0:
+      printInfo(&"  PASS {testName}", useColor)
+      passed += 1
+    else:
+      printError(&"  FAIL {testName} (exit {exitCode})", useColor)
+      failed += 1
+    removeDir(tmpDir)
+  echo &"\nResults: {passed} passed, {failed} failed"
+  return if failed > 0: 1 else: 0
+
 proc cmdVersion*(args: seq[string], opts: GlobalOptions): int =
   echo "bux 0.1.0 (bootstrap)"
   return 0
@@ -597,6 +638,7 @@ proc runCli*(args: seq[string]): int =
   of "build": return cmdBuild(cmdArgs, opts)
   of "run": return cmdRun(cmdArgs, opts)
   of "check": return cmdCheck(cmdArgs, opts)
+  of "test": return cmdTest(cmdArgs, opts)
   of "clean": return cmdClean(cmdArgs, opts)
   of "version", "--version", "-v": return cmdVersion(cmdArgs, opts)
   of "help", "--help", "-h":
diff --git a/docs/BuildAndTest.md b/docs/BuildAndTest.md
index 3982225..3cf194e 100644
--- a/docs/BuildAndTest.md
+++ b/docs/BuildAndTest.md
@@ -89,6 +89,9 @@ Output = "Bin"
 ./buxc run
 ./buxc run ./myproject
 
+# Run tests
+./buxc test
+
 # Clean build artifacts
 ./buxc clean
 ```
diff --git a/library/runtime/runtime.c b/library/runtime/runtime.c
index d210304..3f03c3e 100644
--- a/library/runtime/runtime.c
+++ b/library/runtime/runtime.c
@@ -1324,6 +1324,20 @@ const char* bux_socket_error(void) {
     return strerror(errno);
 }
 
+/* ============================================================================
+ * Test / Assert primitives
+ * ============================================================================ */
+
+void bux_exit(int code) {
+    exit(code);
+}
+
+void bux_assert(int cond, const char* file, int line, const char* expr) {
+    if (!cond) {
+        fprintf(stderr, "ASSERT FAILED: %s at %s:%d\n", expr, file, line);
+        exit(1);
+    }
+}
 
 /* ============================================================================
  * Cryptography primitives (OpenSSL)
diff --git a/library/std/Test.bux b/library/std/Test.bux
new file mode 100644
index 0000000..7cdfcf2
--- /dev/null
+++ b/library/std/Test.bux
@@ -0,0 +1,44 @@
+module Std::Test {
+
+extern func bux_exit(code: int);
+extern func bux_assert(cond: int, file: String, line: int, expr: String);
+
+func Test_Exit(code: int) {
+    bux_exit(code);
+}
+
+func Test_Assert(cond: bool) {
+    bux_assert(cond as int, "", 0, "");
+}
+
+func Test_AssertEqInt(a: int, b: int) {
+    if a != b {
+        PrintLine("ASSERT_EQ FAILED:");
+        PrintInt(a);
+        PrintLine(" != ");
+        PrintInt(b);
+        bux_exit(1);
+    }
+}
+
+func Test_AssertTrue(cond: bool) {
+    if !cond {
+        PrintLine("ASSERT_TRUE FAILED");
+        bux_exit(1);
+    }
+}
+
+func Test_AssertFalse(cond: bool) {
+    if cond {
+        PrintLine("ASSERT_FALSE FAILED");
+        bux_exit(1);
+    }
+}
+
+func Test_Fail(msg: String) {
+    PrintLine("FAIL:");
+    PrintLine(msg);
+    bux_exit(1);
+}
+
+}