Description
Tests in Rust
Rust supports writing software tests to ensure the correctness of the code. There are three styles for
testing: Unit testing, Doc testing, and Integration testing. Moreover, Rust supports specifying
Dev-dependencies.
Tests are functions that are written to verify that the non-test code is running properly. The structure of a
test function typically involves some setup, run the “non-test code” you wish to test, then assert
whether the results are what we expect.
Unit tests should be combined into a test mod with the #[cfg(test)] attribute. To define test functions,
functions should be marked with the #[test] attribute before the function definition. For example, look at
the following code:
pub fn add(a: i32, b: i32) -> i32 {
a + b
}
// This is a really bad adding function
#[allow(dead_code)]
fn bad_add(a: i32, b: i32) -> i32 {
a – b
}
#[cfg(test)]
mod tests {
// Note this useful idiom: importing names from outer scope.
use super::*;
#[test]
fn test_add() {
assert_eq!(add(1, 2), 3);
}
#[test]
fn test_bad_add() {
// This assert would fire and test will fail.
// Please note, that private functions can be tested too!
assert_eq!(bad_add(1, 2), 3);
}
}
Tests can be run with cargo test.
$ cargo test
running 2 tests
test tests::test_bad_add … FAILED
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ECE 522 | Software Construction, Verification and Evolution
test tests::test_add … ok
failures:
—- tests::test_bad_add stdout —-
thread ‘tests::test_bad_add’ panicked at ‘assertion failed:
`(left == right)`
left: `-1`,
right: `3`’, src/lib.rs:21:8
note: Run with `RUST_BACKTRACE=1` for a backtrace.
failures:
tests::test_bad_add
test result: FAILED. 1 passed; 1 failed; 0 ignored; 0 measured; 0
filtered out
Question 1:
Source code: UTApp.zip
The application provides 4 test modules, question1, question2, question3, and question4.
a- Implement the functionality defined by question1 to pass all the tests in this module. Your task is
to define the functions add and subtract in the calculator.rs file.
b- Running the tests in question2.rs will pass with no problems because there no actual tests in the
file. Your task is to write the functionality defined by the tests (multiply and divide functions) and
write the tests cases for your code to test these two functions.
c- Implement the functionality defined by question3 to pass all the tests in this module. Your task is
to define the functions get_square_root in the calculator.rs file. Then write the code for the four
test functions defined in question3.
d- Implement the functionality defined by question4 to pass all the tests in this module. Your task is
to define the functions get_roots to calculate the roots for quadratic equations. Then, you need
to write the code for four tests functions defined in question4.
Question 2:
Hamcrest is a framework for defining ‘match’ rules and designing matcher objects. When writing tests, it
could be challenging to have the right balance between over-specifying the test (and making it brittle to
changes), and not specifying enough (making the test less valuable since it continues to pass even when
the thing being tested is broken).
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ECE 522 | Software Construction, Verification and Evolution
Having a tool that allows you to pick out precisely the aspect under test and describe the values it should
have, to a controlled level of precision, helps significantly in writing tests that are “just right”. Such tests
fail when the behavior of the aspect under test deviates from the expected behavior, yet continue to
pass when minor, unrelated changes to the behavior are made.
Let us assume we have a struct for a player instance as follows:
struct Player {
id: i32,
first_name: String,
last_name: String,
}
Use the Hamcrest framework (i.e. use a hamcrest crate) to write tests that assert that:
a- The properties of Player called last_name and first_name are of type String.
b- Two Players created with the same id, have the same first name and last name.
Question 3: Redo question 1 using the Hamcrest framework. Submit your code as UTApp_hamcrest.
Question 4: Combination function algorithm
a- Write a program that finds the value of the combination function, c(a, b) where a and b are both
read as user input (Hint: you may need to use io::stdin().read_line()). Combination function is
defined as:
𝑐(𝑎, 𝑏) =
𝑎!
(𝑎−𝑏)!𝑏!
b- Write a test that ensures a is not smaller than b.
c- Write a test that ensures both a and b are positive integers (Hint: use should_panic)
Question 5: Write a tax() function that calculates the taxed income based on the following table:
Income Tax Rate (%)
0 ≤ income < 10,000 0
10,000 ≤ income < 50,000 10
50,000 ≤ income < 100,000 20
100,000 ≤ income < 1,000,000 30
Income ≥ 1,000,000 40
The function should return the taxed income as:
Taxed_income = income – (income * tax_rate)
Write tests that ensure that your code can handle the following error conditions (Hint: use
should_panic):
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ECE 522 | Software Construction, Verification and Evolution
– Income is a negative number.
– Income is not an integer.
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