diff --git a/.gitignore b/.gitignore
new file mode 100644
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+autotests/passwords.h
diff --git a/CMakeLists.txt b/CMakeLists.txt
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -82,4 +82,6 @@
   DESTINATION ${KDE_INSTALL_INCLUDEDIR_KF5} COMPONENT Devel
 )
 
+add_subdirectory(autotests)
+
 feature_summary(WHAT ALL   FATAL_ON_MISSING_REQUIRED_PACKAGES)
diff --git a/autotests/CMakeLists.txt b/autotests/CMakeLists.txt
new file mode 100644
--- /dev/null
+++ b/autotests/CMakeLists.txt
@@ -0,0 +1,3 @@
+include(ECMAddTests)
+find_package(Qt5Test REQUIRED)
+ecm_add_test(kdesutest.cpp ${ARGV1} TEST_NAME kdesutest LINK_LIBRARIES Qt5::Test KF5::Su KF5::CoreAddons KF5::Service)
diff --git a/autotests/kdesutest.cpp b/autotests/kdesutest.cpp
new file mode 100644
--- /dev/null
+++ b/autotests/kdesutest.cpp
@@ -0,0 +1,74 @@
+
+#include <QObject>
+#include <QTest>
+#include <../src/suprocess.h>
+#include <QString>
+
+#include <kconfig.h>
+#include <kconfiggroup.h>
+#include <ksharedconfig.h>
+
+// add this yourself, should include
+// #define MYPASSWORD "foo"
+// #define ROOTPASSWORD "bar"
+#include "passwords.h"
+
+namespace KDESu
+{
+
+class KdeSuTest: public QObject
+{
+    Q_OBJECT
+private Q_SLOTS:
+    void initTestCase() { 
+    }
+    void sudoGoodPassword() {
+        KSharedConfig::Ptr config = KSharedConfig::openConfig();
+        KConfigGroup group(config, "super-user-command");
+        group.writeEntry("super-user-command", "sudo");
+
+        KDESu::SuProcess* suProcess = new KDESu::SuProcess("root", "ls");
+        QString suapp = suProcess->superUserCommand();
+        QVERIFY(suapp==QLatin1String("sudo"));
+        int result = suProcess->exec(MYPASSWORD, 0);
+        QVERIFY(result == KDESu::SuProcess::ok);
+    }
+    void sudoBadPassword() {
+        KSharedConfig::Ptr config = KSharedConfig::openConfig();
+        KConfigGroup group(config, "super-user-command");
+        group.writeEntry("super-user-command", "sudo");
+
+        KDESu::SuProcess* suProcess = new KDESu::SuProcess("root", "ls");
+        QString suapp = suProcess->superUserCommand();
+        QVERIFY(suapp==QLatin1String("sudo"));
+        int result2 = suProcess->exec("broken", 0);
+        QVERIFY(result2 == KDESu::SuProcess::SuIncorrectPassword);
+    }
+    void suGoodPassword() {
+        KSharedConfig::Ptr config = KSharedConfig::openConfig();
+        KConfigGroup group(config, "super-user-command");
+        group.writeEntry("super-user-command", "su");
+
+        KDESu::SuProcess* suProcess = new KDESu::SuProcess("root", "ls");
+        QString suapp = suProcess->superUserCommand();
+        QVERIFY(suapp==QLatin1String("su"));
+        int result2 = suProcess->exec(ROOTPASSWORD, 0);
+        QVERIFY(result2 == KDESu::SuProcess::ok);
+    }
+    void suBadPassword() {
+        KSharedConfig::Ptr config = KSharedConfig::openConfig();
+        KConfigGroup group(config, "super-user-command");
+        group.writeEntry("super-user-command", "su");
+
+        KDESu::SuProcess* suProcess = new KDESu::SuProcess("root", "ls");
+        QString suapp = suProcess->superUserCommand();
+        QVERIFY(suapp==QLatin1String("su"));
+        int result2 = suProcess->exec("broken", 0);
+        QVERIFY(result2 == KDESu::SuProcess::SuIncorrectPassword);
+    }
+};
+}
+
+#include <kdesutest.moc>
+QTEST_MAIN(KDESu::KdeSuTest)
+
diff --git a/src/suprocess.h b/src/suprocess.h
--- a/src/suprocess.h
+++ b/src/suprocess.h
@@ -72,6 +72,7 @@
     void virtual_hook(int id, void *data) Q_DECL_OVERRIDE;
 
 private:
+    friend class KdeSuTest;
     enum SuErrors {
         error = -1,
         ok = 0,
diff --git a/src/suprocess.cpp b/src/suprocess.cpp
--- a/src/suprocess.cpp
+++ b/src/suprocess.cpp
@@ -24,6 +24,8 @@
 #include <kconfiggroup.h>
 #include <ksharedconfig.h>
 #include <kuser.h>
+#include <QDebug>
+#include <QLoggingCategory>
 
 #ifdef KDESU_USE_SUDO_DEFAULT
 #  define DEFAULT_SUPER_USER_COMMAND QStringLiteral("sudo")
@@ -41,6 +43,8 @@
     QString superUserCommand;
 };
 
+static QLoggingCategory category("org.kde.kdesu");
+
 SuProcess::SuProcess(const QByteArray &user, const QByteArray &command)
     : d(new SuProcessPrivate)
 {
@@ -203,7 +207,8 @@
     QByteArray line;
     while (true) {
         line = readLine();
-        if (line.isNull()) {
+        // return if problem. sudo checks for a second prompt || su gets a blank line
+        if ((line.contains(':') && state != WaitForPrompt) || line.isNull()) {
             return (state == HandleStub ? notauthorized : error);
         }