setUp and tearDown
- Dart course
- Intermediate
- Lesson 85/116
- 5 min
Learn fixtures with setUp and tearDown.
setUp and tearDown
setUp(() { ... }) runs before each test, tearDown(() { ... }) runs after each test. This prepares a clean environment (fixture) for each test.
For example a Counter instance created in setUp lets every test start fresh. tearDown closes temporary files or connections.
These methods can be used inside a group; they then run only for that group's tests.
The fixture concept
A fixture is the environment a test runs in. In setUp you create an object and place it in a variable shared by tests. Each test receives it fresh.
For example late Counter c; setUp(() { c = Counter(); }); produces a new Counter for each test. Tests no longer affect each other.
tearDown cleans up at the end; it deletes temp files or closes connections.
Practice The Counter class
Define a Counter class with an int value = 0 field and a void increment() => value++ method. In main create a Counter, call increment() three times and print value with print.
Starter code
// Define the Counter class (value, increment)
void main() {
// create a Counter, call increment three times, print value
}Sample solution
class Counter {
int value = 0;
void increment() => value++;
}
void main() {
var c = Counter();
c.increment();
c.increment();
c.increment();
print(c.value);
}Expected output
3
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 When does setUp run?
- Once after all tests
- Once at program start
- Only on error
- Before each test Correct answer
Explanation: setUp runs before each test.
2 The setUp block
____(() {
counter = Counter();
});setUp(() {
counter = Counter();
});Explanation: setUp runs code before each test.
3 Fixture parts
| Term | Meaning |
|---|---|
setUp |
Before test |
tearDown |
After test |
Counter() |
Fixture object |
value |
Tested field |