diff --git a/.gitignore b/.gitignore
index cb50d2d..a6db308 100644
--- a/.gitignore
+++ b/.gitignore
@@ -54,4 +54,4 @@ dkms.conf
 
 main
 
-*result.txt
\ No newline at end of file
+*results.txt
\ No newline at end of file
diff --git a/MMS24-25.c b/MMS24-25.c
index 1f08442..93770d0 100644
--- a/MMS24-25.c
+++ b/MMS24-25.c
@@ -24,30 +24,41 @@
 #define NULL 0
 #endif
 
-void _error(char* fmt,...) {
-    printf("<\x1B[31;1m ERROR \x1B[0m: \x1B[34m'");
+void _error(char* fmt, ...) {
+    fprintf(stderr, "<\x1B[31;1m ERROR \x1B[0m: \x1B[34m'");
 
     va_list args;
     va_start(args, fmt);
-    printf(fmt, args);
+    vfprintf(stderr, fmt, args);
     va_end(args);
 
-    printf("'\x1B[0m >\n");
+    fprintf(stderr, "'\x1B[0m >\n");
 
+#ifndef _TESTS_NONSTOP
     exit(-1);
+#endif
 }
 
-void _debug(char* fmt,...) {
-    printf("[\x1B[31;1m DEBUG \x1B[0m] \x1B[34m'");
+void _debug(char* fmt, ...) {
+    fprintf(stderr, "[\x1B[31;1m DEBUG \x1B[0m] \x1B[34m'");
 
     va_list args;
     va_start(args, fmt);
-    printf(fmt, args);
+    vfprintf(stderr, fmt, args);
     va_end(args);
 
-    printf("'\x1B[0m\n");
+    fprintf(stderr, "'\x1B[0m\n");
+}
 
-    exit(-1);
+void _warn(char* fmt, ...) {
+    fprintf(stderr, "[\x1B[33;1m WARN \x1B[0m] \x1B[34m'");
+
+    va_list args;
+    va_start(args, fmt);
+    vfprintf(stderr, fmt, args);
+    va_end(args);
+
+    fprintf(stderr, "'\x1B[0m\n");
 }
 
 double interpolateLine(
@@ -102,9 +113,22 @@ double *generateSineValues(
     ) {
     /* Generate an array of `iNumValues` double value, so that the values
      * represent the Y-coordinates of a sine curve of which one full period
-     * occupies `iNumSamplesPerPeriod` values
+     * occupies `iNumSamplesPerPeriod` values.
      */
 
+    if (iNumSamplesPerPeriod == 0)
+        _error("*generateSineValues: iNumSamplesPerPeriod must be non-0!");
+
+    if (iNumSamplesPerPeriod < 0)
+        _warn("*generateSineValues: iNumSamplesPerPeriod is less than 0!");
+
+    if (iNumValues < 0)
+        _error("*generateSineValues: iNumValues must be equal to or greater than 0!");
+
+    if (iNumValues == 0)
+        _warn("*generateSineValues: iNumValues is 0!");
+
+
     // Initialize the output array
     double* sineArray = NULL;
     sineArray = (double*) malloc(sizeof(double) * iNumValues);
@@ -120,9 +144,7 @@ double *generateSineValues(
 }
 
 void writeDoubleArray(double *pdOut, int iLen, char *pcOutName) {
-    /* Write a list of double values to a file
-     */
-
+    // Write a list of double values to a file
     FILE* datei = fopen(pcOutName, "w");
     if (datei == NULL)
         _error("writeDoubleArray: Error while opening file '%s'.\n", pcOutName);
diff --git a/Makefile b/Makefile
index b36eebb..1b5c3d8 100644
--- a/Makefile
+++ b/Makefile
@@ -1,6 +1,6 @@
 CC=gcc
 SOURCE_FILE=MMS24-25.c
-OPTS=-lm
+OPTS=-lm -D _TESTS_NONSTOP
 
 all: clean tests run
 
diff --git a/tests b/tests
deleted file mode 100755
index 0b0af51..0000000
Binary files a/tests and /dev/null differ
diff --git a/tests.c b/tests.c
index f45de54..d7f0fca 100644
--- a/tests.c
+++ b/tests.c
@@ -9,44 +9,44 @@
 #include <math.h>
 
 void info(char* fmt,...) {
-    printf("[\x1B[37;1m INFO \x1B[0m]\t\x1B[34m'");
+    fprintf(stderr, "[\x1B[37;1m INFO \x1B[0m] \x1B[34m'");
 
     va_list args;
     va_start(args, fmt);
-    vprintf(fmt, args);
+    vfprintf(stderr, fmt, args);
     va_end(args);
 
-    printf("'\x1B[0m\n");
+    fprintf(stderr, "'\x1B[0m\n");
 }
 
 void success(char* fmt,...) {
-    printf("[\x1B[32;1m SUCCESS \x1B[0m]\t\x1B[34m'");
+    fprintf(stderr, "[\x1B[32;1m PASS \x1B[0m] \x1B[34m'");
 
     va_list args;
     va_start(args, fmt);
-    vprintf(fmt, args);
+    vfprintf(stderr, fmt, args);
     va_end(args);
 
-    printf("'\x1B[0m\n");
+    fprintf(stderr, "'\x1B[0m\n");
 }
 
 void error(const char* fmt, ...) {
     va_list args;
 
-    printf("<\x1B[31;1m ERROR \x1B[0m: \x1B[34m'");
+    fprintf(stderr, "<\x1B[31;1m ERROR \x1B[0m: \x1B[34m'");
     va_start(args, fmt);
-    vprintf(fmt, args);
+    vfprintf(stderr, fmt, args);
     va_end(args);
-    printf("'\x1B[0m >\n");
+    fprintf(stderr, "'\x1B[0m >\n");
     exit(-1);
 }
 
 void testInterpolation() {
-    info("testInterpolation();");
+    info("testInterpolation");
 
-    double dRangeMin = -10;
-    double dRangeMax = 10;
-    double dRangeStep = 0.5;
+    double dRangeMin = -3;
+    double dRangeMax = 3;
+    double dRangeStep = 0.33;
 
     for (double dX1=dRangeMin;dX1<dRangeMax;dX1+=dRangeStep) {
         for (double dX2=dRangeMin;dX2<dRangeMax;dX2+=dRangeStep) {
@@ -70,8 +70,47 @@ void testInterpolation() {
     success("testInterpolation();");
 }
 
+void testSineAndWriteDoubleArraySingle(int nValues, int dPLen, double dAmp) {
+    info("Trying: %d, %d, %lf", nValues, dPLen, dAmp);
+
+    char* fileName = NULL;
+    fileName = malloc(100*sizeof(char));
+
+    if (fileName == NULL) {
+        error("Could not allocate Memory for `fileName`!");
+    }
+
+    sprintf(fileName, "sine_%d_%d_%lf.results.txt", nValues, dPLen, dAmp);
+
+    writeDoubleArray(
+        generateSineValues(
+            nValues,
+            dPLen,
+            dAmp
+        ),
+        nValues,
+        fileName
+    );
+
+    info("use `plot \"%s\", \"%s\" with lines` to view.", fileName, fileName);
+
+    free(fileName);
+}
+
+void testSineAndWriteDoubleArray() {
+    info("testSineAndWriteDoubleArray");
+    
+    testSineAndWriteDoubleArraySingle(1000, 300, 1);
+    testSineAndWriteDoubleArraySingle(10, 10, 0.5);
+    testSineAndWriteDoubleArraySingle(10, -10, 0.5);
+    testSineAndWriteDoubleArraySingle(10, 10, 0);
+
+    success("testSineAndWriteDoubleArray");
+}
+
 int main (int iArgC, char** ppcArgV){
     testInterpolation();
+    testSineAndWriteDoubleArray();
 
     return 0;
 }