From 912644d84172d74c1e0a3b1da0ae7a57ca2c3572 Mon Sep 17 00:00:00 2001
From: Tobias Berger <berger@edv-ermtraud.net>
Date: Tue, 21 Sep 2021 10:42:04 +0200
Subject: [PATCH] Improve test_constructor, add custom error

---
 fraction.cpp         |  4 ++--
 fraction.hpp         |  5 +++++
 tst_fractiontest.cpp | 15 ++++++++++++---
 3 files changed, 19 insertions(+), 5 deletions(-)

diff --git a/fraction.cpp b/fraction.cpp
index 21f79f0..2a6c09d 100644
--- a/fraction.cpp
+++ b/fraction.cpp
@@ -40,7 +40,7 @@ namespace FractionNS {
 
   Fraction::Fraction(int numerator, int denominator)
   {
-    if(denominator == 0) throw std::range_error("Tried to divide by 0.");
+    if(denominator == 0) throw divide_by_zero_error();
     this->m_numerator = numerator;
     this->m_denominator = denominator;
     reduce();
@@ -62,7 +62,7 @@ namespace FractionNS {
     this->m_numerator = numerator / gcd;
   }
   void Fraction::setDenominator(int denominator) {
-    if(denominator == 0) throw std::range_error("Tried to divide by 0.");
+    if(denominator == 0) throw divide_by_zero_error();
     auto gcd = FractionNS::gcd(this->m_numerator, denominator);
     this->m_denominator = denominator / gcd;
   }
diff --git a/fraction.hpp b/fraction.hpp
index 43d8ba0..ac988c4 100644
--- a/fraction.hpp
+++ b/fraction.hpp
@@ -3,6 +3,11 @@
 #include <QString>
 
 namespace FractionNS {
+  class divide_by_zero_error : public std::logic_error {
+  public:
+    divide_by_zero_error() : std::logic_error("tried to divide by zero") {};
+  };
+
   class Fraction
   {
   private:
diff --git a/tst_fractiontest.cpp b/tst_fractiontest.cpp
index 62c80e1..57fc24c 100644
--- a/tst_fractiontest.cpp
+++ b/tst_fractiontest.cpp
@@ -60,11 +60,20 @@ void FractionTest::test_constructor() {
 
   // Zero
   Fraction f6 = Fraction(0);
-  QCOMPARE(f6, 0);
+  QCOMPARE(f6.getNumerator(), 0);
   Fraction f7 = Fraction(0, 3);
-  QCOMPARE(f7, 0);
+  QCOMPARE(f7.getNumerator(), 0);
 
-  QCOMPARE(f6, f7);
+  QCOMPARE(f6.getDenominator(), f7.getDenominator());
+
+  // Invalid zero fraction
+  bool threw_divide_by_zero_error = false;
+  try {
+    Fraction(2, 0);
+  }  catch (const divide_by_zero_error&) {
+    threw_divide_by_zero_error = true;
+  }
+  QVERIFY(threw_divide_by_zero_error);
 }
 
 void FractionTest::test_display() {