Enhance Fraction class FromString() and add tests

src/test/util_tests.cpp

@@ -1744,7 +1744,65 @@ BOOST_AUTO_TEST_CASE(util_Fraction_ToString)
     Fraction fraction(123, 10000);
 
     BOOST_CHECK_EQUAL(fraction.IsSimplified(), true);
-    BOOST_CHECK_EQUAL(fraction.ToString(),"123/10000");
+    BOOST_CHECK_EQUAL(fraction.ToString(), "123/10000");
+}
+
+BOOST_AUTO_TEST_CASE(util_Fraction_FromString)
+{
+    Fraction fraction = Fraction().FromString("100/567");
+
+    BOOST_CHECK_EQUAL(fraction.IsSimplified(), true);
+    BOOST_CHECK(fraction == Fraction(100, 567, true));
+
+    fraction = Fraction().FromString("-100/567");
+
+    BOOST_CHECK_EQUAL(fraction.IsSimplified(), true);
+    BOOST_CHECK(fraction == Fraction(-100, 567, true));
+
+    fraction = Fraction().FromString("100/-567");
+
+    BOOST_CHECK_EQUAL(fraction.IsSimplified(), true);
+    BOOST_CHECK(fraction == Fraction(-100, 567, true));
+
+    fraction = Fraction().FromString("5");
+
+    BOOST_CHECK_EQUAL(fraction.IsSimplified(), true);
+    BOOST_CHECK(fraction == Fraction(5, 1, true));
+
+    std::string err;
+    std::string valid_err_message {"fraction input string cannot be parsed to fraction"};
+
+    try {
+        Fraction fraction = Fraction().FromString("100/567/300");
+    } catch (std::out_of_range& e) {
+        err = e.what();
+    }
+
+    BOOST_CHECK_EQUAL(err, valid_err_message);
+
+    try {
+        Fraction fraction = Fraction().FromString("100 / 567");
+    } catch (std::out_of_range& e) {
+        err = e.what();
+    }
+
+    BOOST_CHECK_EQUAL(err, valid_err_message);
+
+    try {
+        Fraction fraction = Fraction().FromString("100.1");
+    } catch (std::out_of_range& e) {
+        err = e.what();
+    }
+
+    BOOST_CHECK_EQUAL(err, valid_err_message);
+
+    try {
+        Fraction fraction = Fraction().FromString("");
+    } catch (std::out_of_range& e) {
+        err = e.what();
+    }
+
+    BOOST_CHECK_EQUAL(err, valid_err_message);
 }
 
 BOOST_AUTO_TEST_SUITE_END()

src/util.h

@@ -344,13 +344,25 @@ class Fraction {
     {
         std::vector<std::string> string_fraction = split(string, "/");
 
+        if (string_fraction.size() > 2 || string_fraction.size() < 1) {
+            throw std::out_of_range("fraction input string cannot be parsed to fraction");
+        }
+
         int64_t numerator;
         int64_t denominator;
 
-        if (string_fraction.size() != 2
-            || !ParseInt64(string_fraction[0], &numerator)
-            || !ParseInt64(string_fraction[1], &denominator)) {
-            throw std::out_of_range("Fraction input string cannot be parsed to fraction.");
+        if (string_fraction.size() == 1) {
+            if (!ParseInt64(string_fraction[0], &numerator)) {
+                throw std::out_of_range("fraction input string cannot be parsed to fraction");
+            }
+
+            denominator = 1;
+        } else {
+            // There must be two elements to the string fraction if we are here.
+            if (!ParseInt64(string_fraction[0], &numerator)
+                || !ParseInt64(string_fraction[1], &denominator)) {
+                throw std::out_of_range("fraction input string cannot be parsed to fraction");
+            }
         }
 
         return Fraction(numerator, denominator, true);