test ln functions for values smaller than 0 and 0

src/exponent.c

@@ -16,7 +16,7 @@ double expI(double e, double num){
 }
 
 double expIN(double e, double num){
-    if(e - ((int) e) < 0.0001 || e - ((int) e) > -0.0001){
+    if(e - ((int) e) < 0.000001 || e - ((int) e) > -0.000001){
         if(e>0){
             return expI(e, num);
         }
@@ -56,6 +56,9 @@ double absD(double x){
 }
 
 double logN(double x, double eps){
+    if(x <= 0){
+        return -1.0;
+    }    
     double yn = x - 1.0;
     double yn1 = yn;
 

test/test_exponent.c

@@ -85,6 +85,21 @@ void test_ln_with_positive_number(void){
     TEST_ASSERT_DOUBLE_WITHIN(0.000001, 0.916290, r3);
 }
 
+void test_ln_with_zero_and_negative_numbers(void){
+    double r1, r2, r3;
+
+    r1 = logN(0.0, 0.000001);
+    r2 = logN(-1.0, 0.000001);
+    r3 = logN(-2.5, 0.000001);
+
+    printf("Result 1: %lf\n", r1);
+    printf("Result 2: %lf\n", r2);
+    printf("Result 3: %lf\n", r3);
+
+    TEST_ASSERT_EQUAL_DOUBLE(-1.0, r1);
+    TEST_ASSERT_EQUAL_DOUBLE(-1.0, r2);
+    TEST_ASSERT_EQUAL_DOUBLE(-1.0, r3);
+}
 
 
 #endif // TEST