diff --git a/tests/cppunit.h b/tests/cppunit.h
index a40aa29..8fe860f 100644
--- a/tests/cppunit.h
+++ b/tests/cppunit.h
@@ -3,6 +3,8 @@
 
 #include "./testutils.h"
 
+#include "../application/commandlineutils.h"
+
 #include <cppunit/TestPath.h>
 #include <cppunit/extensions/TestFactoryRegistry.h>
 #include <cppunit/ui/text/TestRunner.h>
@@ -13,6 +15,18 @@ using namespace std;
 using namespace CppUtilities;
 using namespace CPPUNIT_NS;
 
+/*!
+ * \brief Prints the names of all child tests of the specified \a test.
+ */
+void printTestNames(Test *test, Indentation indentation)
+{
+    for (int index = 0, count = test->getChildTestCount(); index != count; ++index) {
+        const auto childTest = test->getChildTestAt(index);
+        cerr << '\n' << indentation << " - " << childTest->getName();
+        printTestNames(childTest, indentation + 4);
+    }
+}
+
 /*!
  * \brief Performs unit tests using cppunit.
  */
@@ -23,22 +37,41 @@ int main(int argc, char **argv)
         return -1;
     }
 
+    // list tests
+    TestFactoryRegistry &registry = TestFactoryRegistry::getRegistry();
+    if (testApp.onlyListUnits()) {
+        cerr << "Available tests:";
+        printTestNames(registry.makeTest(), Indentation(0));
+        cerr << '\n';
+        return 0;
+    }
+
     // run tests
     TextUi::TestRunner runner;
-    TestFactoryRegistry &registry = TestFactoryRegistry::getRegistry();
     if (!testApp.unitsSpecified() || testApp.units().empty()) {
         // no units specified -> test all
         runner.addTest(registry.makeTest());
     } else {
         // pick specified units from overall test
         Test *overallTest = registry.makeTest();
+        vector<const char *> unavailableUnits;
         for (const char *unit : testApp.units()) {
             try {
                 runner.addTest(overallTest->findTest(unit));
             } catch (const invalid_argument &) {
-                cerr << "The specified test unit \"" << unit << "\" is not available and will be ignored.\n";
+                unavailableUnits.emplace_back(unit);
             }
         }
+        if (!unavailableUnits.empty()) {
+            cerr << "The following tests specified via --unit are not available:";
+            for (const char *unitName : unavailableUnits) {
+                cerr << "\n - " << unitName;
+            }
+            cerr << "\nAvailable tests:";
+            printTestNames(overallTest, Indentation(0));
+            cerr << '\n';
+            return -1;
+        }
     }
     const auto ok = runner.run(string(), false);
     cerr << (ok ? "Tests successful\n" : "Tests failed\n");
diff --git a/tests/testutils.cpp b/tests/testutils.cpp
index 60f5f74..dd62601 100644
--- a/tests/testutils.cpp
+++ b/tests/testutils.cpp
@@ -115,10 +115,12 @@ TestApplication::TestApplication()
  * \throws Throws std::runtime_error if an instance has already been created.
  */
 TestApplication::TestApplication(int argc, const char *const *argv)
-    : m_testFilesPathArg("test-files-path", 'p', "specifies the path of the directory with test files")
-    , m_applicationPathArg("app-path", 'a', "specifies the path of the application to be tested")
-    , m_workingDirArg("working-dir", 'w', "specifies the directory to store working copies of test files")
-    , m_unitsArg("units", 'u', "specifies the units to test; omit to test all units")
+    : m_listArg("list", 'l', "lists available test units")
+    , m_runArg("run", 'r', "runs the tests")
+    , m_testFilesPathArg("test-files-path", 'p', "specifies the path of the directory with test files", { "path" })
+    , m_applicationPathArg("app-path", 'a', "specifies the path of the application to be tested", { "path" })
+    , m_workingDirArg("working-dir", 'w', "specifies the directory to store working copies of test files", { "path" })
+    , m_unitsArg("units", 'u', "specifies the units to test; omit to test all units", { "unit1", "unit2", "unit3" })
 {
     // check whether there is already an instance
     if (m_instance) {
@@ -129,17 +131,11 @@ TestApplication::TestApplication(int argc, const char *const *argv)
     // handle specified arguments (if present)
     if (argc && argv) {
         // setup argument parser
-        for (Argument *arg : initializer_list<Argument *>{ &m_testFilesPathArg, &m_applicationPathArg, &m_workingDirArg }) {
-            arg->setRequiredValueCount(1);
-            arg->setValueNames({ "path" });
-            arg->setCombinable(true);
-        }
         m_testFilesPathArg.setRequiredValueCount(Argument::varValueCount);
         m_unitsArg.setRequiredValueCount(Argument::varValueCount);
-        m_unitsArg.setValueNames({ "unit1", "unit2", "unit3" });
-        m_unitsArg.setCombinable(true);
-        m_parser.setMainArguments(
-            { &m_testFilesPathArg, &m_applicationPathArg, &m_workingDirArg, &m_unitsArg, &m_parser.noColorArg(), &m_parser.helpArg() });
+        m_runArg.setImplicit(true);
+        m_runArg.setSubArguments({ &m_testFilesPathArg, &m_applicationPathArg, &m_workingDirArg, &m_unitsArg });
+        m_parser.setMainArguments({&m_listArg, &m_runArg, &m_parser.noColorArg(), &m_parser.helpArg()});
 
         // parse arguments
         try {
diff --git a/tests/testutils.h b/tests/testutils.h
index 8285e13..570820d 100644
--- a/tests/testutils.h
+++ b/tests/testutils.h
@@ -41,6 +41,7 @@ public:
     const char *applicationPath();
     bool unitsSpecified() const;
     const std::vector<const char *> &units() const;
+    bool onlyListUnits() const;
 
     // static read-only accessors
     static const TestApplication *instance();
@@ -51,10 +52,12 @@ private:
     static std::string readTestfilePathFromSrcRef();
 
     ArgumentParser m_parser;
-    Argument m_testFilesPathArg;
-    Argument m_applicationPathArg;
-    Argument m_workingDirArg;
-    Argument m_unitsArg;
+    OperationArgument m_listArg;
+    OperationArgument m_runArg;
+    ConfigValueArgument m_testFilesPathArg;
+    ConfigValueArgument m_applicationPathArg;
+    ConfigValueArgument m_workingDirArg;
+    ConfigValueArgument m_unitsArg;
     std::vector<std::string> m_testFilesPaths;
     std::string m_workingDir;
     bool m_valid;
@@ -129,6 +132,14 @@ inline const std::vector<const char *> &TestApplication::units() const
     return m_unitsArg.values();
 }
 
+/*!
+ * \brief Returns whether the test application should only list available units and not actually run any tests.
+ */
+inline bool TestApplication::onlyListUnits() const
+{
+    return m_listArg.isPresent();
+}
+
 /*!
  * \brief Convenience function to invoke TestApplication::testFilePath().
  * \remarks A TestApplication must be present.