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