diff --git a/tanco/driver.py b/tanco/driver.py
index c17c145..5cfa475 100644
--- a/tanco/driver.py
+++ b/tanco/driver.py
@@ -465,6 +465,19 @@ def do_test(arg):
         except runner.NoTestPlanError:
             runner.error(cfg, ['No challenge selected.',
                               'Use `tanco init`, `tanco test -t file.org`, or set TEST_PLAN environment variable.'])
+        except runner.NoTestsFoundError as e:
+            runner.error(cfg, [str(e),
+                              '',
+                              'For org files, tests should be defined using:',
+                              '  ** TEST testname : title',
+                              '  #+begin_src',
+                              '  > input line',
+                              '  expected output',
+                              '  #+end_src'])
+        except FileNotFoundError as e:
+            runner.error(cfg, [f'Test file not found: {e.filename}',
+                              '',
+                              'Make sure the path is correct and the file exists.'])
         except runner.StopTesting:
             pass
         except Exception:
@@ -531,8 +544,21 @@ def do_run(self, arg):
             runner.run_tests(cfg)
         except runner.NoTestPlanError:
             print("No tests specified. Use --tests PATH or ensure you're in a tanco project.")
+        except runner.NoTestsFoundError as e:
+            print(str(e))
+            print()
+            print('For org files, tests should be defined using:')
+            print('  ** TEST testname : title')
+            print('  #+begin_src')
+            print('  > input line')
+            print('  expected output')
+            print('  #+end_src')
+        except FileNotFoundError as e:
+            print(f'Test file not found: {e.filename}')
+            print()
+            print('Make sure the path is correct and the file exists.')
         except runner.StopTesting:
-            pass # Normal exit after test failure
+            pass  # Normal exit after test failure
         except Exception:
             # handle_unexpected_error already prints traceback
             runner.handle_unexpected_error(cfg)
diff --git a/tanco/runner.py b/tanco/runner.py
index 914d510..c3abed0 100644
--- a/tanco/runner.py
+++ b/tanco/runner.py
@@ -94,6 +94,10 @@ class NoTestPlanError(Exception):
     pass
 
 
+class NoTestsFoundError(Exception):
+    """Raised when a test source exists but contains no tests."""
+
+
 class StopTesting(Exception):
     pass
 
@@ -354,6 +358,14 @@ def run_tests(cfg: Config, names=None):
     challenge = get_challenge(cfg)
     tests = challenge.tests
 
+    # Check for empty tests list
+    if not tests:
+        source = cfg.test_path or cfg.test_plan or 'database'
+        raise NoTestsFoundError(
+            f'No tests found in {source}. '
+            'Make sure the file contains valid test definitions.',
+        )
+
     # Use persistent process mode if restart_cmd is configured
     if cfg.restart_cmd and cfg.restart_expect:
         run_tests_persistent(cfg, tests, names)
@@ -502,8 +514,21 @@ def main(names: list[str]):
     try:
         run_tests(cfg, names)
     except NoTestPlanError:
-        error(cfg, ['No challenge selected.'
+        error(cfg, ['No challenge selected.',
                     'Use `tanco init` or set TEST_PLAN environment variable.'])
+    except NoTestsFoundError as e:
+        error(cfg, [str(e),
+                    '',
+                    'For org files, tests should be defined using:',
+                    '  ** TEST testname : title',
+                    '  #+begin_src',
+                    '  > input line',
+                    '  expected output',
+                    '  #+end_src'])
+    except FileNotFoundError as e:
+        error(cfg, [f'Test file not found: {e.filename}',
+                    '',
+                    'Make sure the path is correct and the file exists.'])
     except StopTesting:
         pass
     except Exception: