Show a warning when testing an empty project without a test suite // Resolve #4278

HISTORY.rst

@@ -18,6 +18,7 @@ PlatformIO Core 6
 
 * Control |UNITTESTING| verbosity with a new multilevel `pio test -v <https://docs.platformio.org/en/latest/core/userguide/cmd_test.html#cmdoption-pio-test-v>`__ command option (`issue #4276 <https://github.com/platformio/platformio-core/issues/4276>`_)
 * Follow symbolic links during searching for the unit test suites (`issue #4288 <https://github.com/platformio/platformio-core/issues/4288>`_)
+* Show a warning when testing an empty project without a test suite (`issue #4278 <https://github.com/platformio/platformio-core/issues/4278>`_)
 * Fixed an issue when the `build_src_flags <https://docs.platformio.org/en/latest/projectconf/section_env_build.html#build-src-flags>`__ option was applied outside the project scope (`issue #4277 <https://github.com/platformio/platformio-core/issues/4277>`_)
 * Fixed an issue with debugging assembly files without preprocessor (".s")
 

platformio/builder/tools/platformio.py

@@ -165,11 +165,17 @@ def ProcessProjectDeps(env):
             "$BUILD_SRC_DIR", "$PROJECT_SRC_DIR", env.get("SRC_FILTER")
         )
 
-    if not env.get("PIOBUILDFILES") and not COMMAND_LINE_TARGETS:
-        sys.stderr.write(
-            "Error: Nothing to build. Please put your source code files "
-            "to the '%s' folder\n" % env.subst("$PROJECT_SRC_DIR")
-        )
+    if not env.get("PIOBUILDFILES"):
+        if not COMMAND_LINE_TARGETS:
+            sys.stderr.write(
+                "Error: Nothing to build. Please put your source code files "
+                "to the '%s' folder\n" % env.subst("$PROJECT_SRC_DIR")
+            )
+        elif "test" in env.GetBuildType():
+            sys.stderr.write(
+                "Error: Nothing to build. Please put your test suites "
+                "to the '%s' folder\n" % env.subst("$PROJECT_TEST_DIR")
+            )
         env.Exit(1)
 
     Export("projenv")