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29
30
31 // This sample shows how to test common properties of multiple
32 // implementations of the same interface (aka interface tests).
33
34 // The interface and its implementations are in this header.
35 #include "prime_tables.h"
36
37 #include "gtest/gtest.h"
38 namespace {
39 // First, we define some factory functions for creating instances of
40 // the implementations. You may be able to skip this step if all your
41 // implementations can be constructed the same way.
42
43 template <class T>
44 PrimeTable* CreatePrimeTable();
45
46 template <>
CreatePrimeTable()47 PrimeTable* CreatePrimeTable<OnTheFlyPrimeTable>() {
48 return new OnTheFlyPrimeTable;
49 }
50
51 template <>
CreatePrimeTable()52 PrimeTable* CreatePrimeTable<PreCalculatedPrimeTable>() {
53 return new PreCalculatedPrimeTable(10000);
54 }
55
56 // Then we define a test fixture class template.
57 template <class T>
58 class PrimeTableTest : public testing::Test {
59 protected:
60 // The ctor calls the factory function to create a prime table
61 // implemented by T.
PrimeTableTest()62 PrimeTableTest() : table_(CreatePrimeTable<T>()) {}
63
~PrimeTableTest()64 ~PrimeTableTest() override { delete table_; }
65
66 // Note that we test an implementation via the base interface
67 // instead of the actual implementation class. This is important
68 // for keeping the tests close to the real world scenario, where the
69 // implementation is invoked via the base interface. It avoids
70 // got-yas where the implementation class has a method that shadows
71 // a method with the same name (but slightly different argument
72 // types) in the base interface, for example.
73 PrimeTable* const table_;
74 };
75
76 using testing::Types;
77
78 // Google Test offers two ways for reusing tests for different types.
79 // The first is called "typed tests". You should use it if you
80 // already know *all* the types you are gonna exercise when you write
81 // the tests.
82
83 // To write a typed test case, first use
84 //
85 // TYPED_TEST_SUITE(TestCaseName, TypeList);
86 //
87 // to declare it and specify the type parameters. As with TEST_F,
88 // TestCaseName must match the test fixture name.
89
90 // The list of types we want to test.
91 typedef Types<OnTheFlyPrimeTable, PreCalculatedPrimeTable> Implementations;
92
93 TYPED_TEST_SUITE(PrimeTableTest, Implementations);
94
95 // Then use TYPED_TEST(TestCaseName, TestName) to define a typed test,
96 // similar to TEST_F.
TYPED_TEST(PrimeTableTest,ReturnsFalseForNonPrimes)97 TYPED_TEST(PrimeTableTest, ReturnsFalseForNonPrimes) {
98 // Inside the test body, you can refer to the type parameter by
99 // TypeParam, and refer to the fixture class by TestFixture. We
100 // don't need them in this example.
101
102 // Since we are in the template world, C++ requires explicitly
103 // writing 'this->' when referring to members of the fixture class.
104 // This is something you have to learn to live with.
105 EXPECT_FALSE(this->table_->IsPrime(-5));
106 EXPECT_FALSE(this->table_->IsPrime(0));
107 EXPECT_FALSE(this->table_->IsPrime(1));
108 EXPECT_FALSE(this->table_->IsPrime(4));
109 EXPECT_FALSE(this->table_->IsPrime(6));
110 EXPECT_FALSE(this->table_->IsPrime(100));
111 }
112
TYPED_TEST(PrimeTableTest,ReturnsTrueForPrimes)113 TYPED_TEST(PrimeTableTest, ReturnsTrueForPrimes) {
114 EXPECT_TRUE(this->table_->IsPrime(2));
115 EXPECT_TRUE(this->table_->IsPrime(3));
116 EXPECT_TRUE(this->table_->IsPrime(5));
117 EXPECT_TRUE(this->table_->IsPrime(7));
118 EXPECT_TRUE(this->table_->IsPrime(11));
119 EXPECT_TRUE(this->table_->IsPrime(131));
120 }
121
TYPED_TEST(PrimeTableTest,CanGetNextPrime)122 TYPED_TEST(PrimeTableTest, CanGetNextPrime) {
123 EXPECT_EQ(2, this->table_->GetNextPrime(0));
124 EXPECT_EQ(3, this->table_->GetNextPrime(2));
125 EXPECT_EQ(5, this->table_->GetNextPrime(3));
126 EXPECT_EQ(7, this->table_->GetNextPrime(5));
127 EXPECT_EQ(11, this->table_->GetNextPrime(7));
128 EXPECT_EQ(131, this->table_->GetNextPrime(128));
129 }
130
131 // That's it! Google Test will repeat each TYPED_TEST for each type
132 // in the type list specified in TYPED_TEST_SUITE. Sit back and be
133 // happy that you don't have to define them multiple times.
134
135 using testing::Types;
136
137 // Sometimes, however, you don't yet know all the types that you want
138 // to test when you write the tests. For example, if you are the
139 // author of an interface and expect other people to implement it, you
140 // might want to write a set of tests to make sure each implementation
141 // conforms to some basic requirements, but you don't know what
142 // implementations will be written in the future.
143 //
144 // How can you write the tests without committing to the type
145 // parameters? That's what "type-parameterized tests" can do for you.
146 // It is a bit more involved than typed tests, but in return you get a
147 // test pattern that can be reused in many contexts, which is a big
148 // win. Here's how you do it:
149
150 // First, define a test fixture class template. Here we just reuse
151 // the PrimeTableTest fixture defined earlier:
152
153 template <class T>
154 class PrimeTableTest2 : public PrimeTableTest<T> {
155 };
156
157 // Then, declare the test case. The argument is the name of the test
158 // fixture, and also the name of the test case (as usual). The _P
159 // suffix is for "parameterized" or "pattern".
160 TYPED_TEST_SUITE_P(PrimeTableTest2);
161
162 // Next, use TYPED_TEST_P(TestCaseName, TestName) to define a test,
163 // similar to what you do with TEST_F.
TYPED_TEST_P(PrimeTableTest2,ReturnsFalseForNonPrimes)164 TYPED_TEST_P(PrimeTableTest2, ReturnsFalseForNonPrimes) {
165 EXPECT_FALSE(this->table_->IsPrime(-5));
166 EXPECT_FALSE(this->table_->IsPrime(0));
167 EXPECT_FALSE(this->table_->IsPrime(1));
168 EXPECT_FALSE(this->table_->IsPrime(4));
169 EXPECT_FALSE(this->table_->IsPrime(6));
170 EXPECT_FALSE(this->table_->IsPrime(100));
171 }
172
TYPED_TEST_P(PrimeTableTest2,ReturnsTrueForPrimes)173 TYPED_TEST_P(PrimeTableTest2, ReturnsTrueForPrimes) {
174 EXPECT_TRUE(this->table_->IsPrime(2));
175 EXPECT_TRUE(this->table_->IsPrime(3));
176 EXPECT_TRUE(this->table_->IsPrime(5));
177 EXPECT_TRUE(this->table_->IsPrime(7));
178 EXPECT_TRUE(this->table_->IsPrime(11));
179 EXPECT_TRUE(this->table_->IsPrime(131));
180 }
181
TYPED_TEST_P(PrimeTableTest2,CanGetNextPrime)182 TYPED_TEST_P(PrimeTableTest2, CanGetNextPrime) {
183 EXPECT_EQ(2, this->table_->GetNextPrime(0));
184 EXPECT_EQ(3, this->table_->GetNextPrime(2));
185 EXPECT_EQ(5, this->table_->GetNextPrime(3));
186 EXPECT_EQ(7, this->table_->GetNextPrime(5));
187 EXPECT_EQ(11, this->table_->GetNextPrime(7));
188 EXPECT_EQ(131, this->table_->GetNextPrime(128));
189 }
190
191 // Type-parameterized tests involve one extra step: you have to
192 // enumerate the tests you defined:
193 REGISTER_TYPED_TEST_SUITE_P(
194 PrimeTableTest2, // The first argument is the test case name.
195 // The rest of the arguments are the test names.
196 ReturnsFalseForNonPrimes, ReturnsTrueForPrimes, CanGetNextPrime);
197
198 // At this point the test pattern is done. However, you don't have
199 // any real test yet as you haven't said which types you want to run
200 // the tests with.
201
202 // To turn the abstract test pattern into real tests, you instantiate
203 // it with a list of types. Usually the test pattern will be defined
204 // in a .h file, and anyone can #include and instantiate it. You can
205 // even instantiate it more than once in the same program. To tell
206 // different instances apart, you give each of them a name, which will
207 // become part of the test case name and can be used in test filters.
208
209 // The list of types we want to test. Note that it doesn't have to be
210 // defined at the time we write the TYPED_TEST_P()s.
211 typedef Types<OnTheFlyPrimeTable, PreCalculatedPrimeTable>
212 PrimeTableImplementations;
213 INSTANTIATE_TYPED_TEST_SUITE_P(OnTheFlyAndPreCalculated, // Instance name
214 PrimeTableTest2, // Test case name
215 PrimeTableImplementations); // Type list
216
217 } // namespace
218