Exercise 1: Testing the Tester
As you may recall from the reading, MediaScript provides four primary
testing procedures:
(begin-tests!), which prepares
the environment for testing.
(test! expression
value), which determines (a)
whether expression can be successfully
evaluated and, if so, (b) whether the value
of expression is value.
(test-error! expression),
which determines whether or not expression
reports an error (and treats it as a problem
if expression does not).
(end-tests!), which reports on
the tests completed so far.
a. In the Interactions pane, try each of the operations a few times
to make sure you understand its operation. (Yes, this instruction is
intentionally vague.)
b. What happens if you call end-tests! multiple
times, perhaps with some intervening calls to test!
or test-error! but with no intervening calls to
begin-tests!?
Exercise 2: Testing Triangulation
Consider the following procedure documentation:
;;; Procedure:
;;; classify-triangle
;;; Parameters:
;;; side1, a real number [unverified]
;;; side2, a real number [unverified]
;;; side3, a real number [unverified]
;;; Purpose:
;;; Determine the kind of triangle the three sides describe.
;;; Produces:
;;; classification, a string
;;; Preconditions:
;;; side1, side2, and side3 together describe a triangle [verified]
;;; Postconditions:
;;; If all three sides are equal, classification is "equilateral".
;;; If exactly two sides are equal, classification is "isosceles".
;;; If no two sides are equal, classification is "scalene".
a. Write a series of tests for this procedure. Your tests should
look something like the following:
(load "/home/davisjan/csc/151/examples/triangles/tri.0000.sct")
(begin-tests!)
(test! (classify-triangle 1 1 1) "equilateral")
...
(end-tests!)
b. There are approximately 40 different versions of the procedure of
varying degrees of correctness. (Professor Rebelsky wrote a program to
create them!) They are named as follows (and all appear in the same
directory as tri.0000.sct):
tri.0000.sct,
tri.0001.sct,
tri.0010.sct,
tri.0011.sct,
tri.0100.sct,
tri.0101.sct,
tri.0110.sct,
tri.0111.sct,
tri.0200.sct,
tri.0201.sct,
tri.0210.sct,
tri.0211.sct,
tri.1000.sct,
tri.1001.sct,
tri.1010.sct,
tri.1011.sct,
tri.1100.sct,
tri.1101.sct,
tri.1110.sct,
tri.1111.sct,
tri.1200.sct,
tri.1201.sct,
tri.1210.sct,
tri.1211.sct,
tri.2000.sct,
tri.2001.sct,
tri.2010.sct,
tri.2011.sct,
tri.2100.sct,
tri.2101.sct,
tri.2110.sct,
tri.2111.sct,
tri.2200.sct,
tri.2201.sct,
tri.2210.sct, and
tri.2211.sct
Pick eight or so of those files and run your tests on them. Which ones
pass your tests? (Try to collaborate with your classmates so that
all of them get tested.)
Exercise 3: Writing a Triangle Classifier
a. To the best of your ability, write
the classify-triangle procedure described in the previous
problem.
b. Rerun your tests using this version of the procedure. How many does
it pass, how many does it fail? Do not rewrite the procedure to make
it pass all these tests.
Exercise 4: A Simple Test Suite
Here is a test that someone might write for the procedure
described above.
(load "/home/davisjan/csc/151/examples/triangles/tri.0000.sct")
(begin-tests!)
(test! (classify-triangle 1 1 1) "equilateral")
(test! (classify-triangle 2 2 3) "isosceles")
(test! (classify-triangle 3 4 5) "scalene")
(end-tests!)
a. Does your classify-triangle procedure pass
these tests? If not, repair it to ensure that it passes all the
tests.
b. Run this test suite on five of the variants mentioned in problem
2 that you have either not tested or that have passed all tests so
far. How many pass the new test suite?
c. Can you write an obvious solution to classify-triangle
that passes all of these tests, but fails to meet the specifications?
Exercise 5: Testing Error Checking
Someone thinking carefully about the definition of
classify-triangle might worry that the tests,
as written, do not check for non-triangles. For example, something
with side lengths 1, 1, and 3 is not a triangle.
a. Add a test to the testing code above to ensure that
classify-triangle rejects that non-triangle.
b. Does your version of classify-triangle pass the
revised test suite? If not, correct it so that it does.
c. Run this test suite on five of the variants mentioned in Exercise 2
that you have either not tested or that have passed all tests so
far. How many pass the new test suite?
Exercise 6: Testing Error Checking, Revisited
Another set of inputs for
which classify-triangle is supposed to fail is
one in which any of the side lengths are negative.
a. Add tests to the test suite
for classify-triangle to ensure
that classify-triangle rejects any set of three
numbers that include a zero or negative number.
b. Does your version of classify-triangle pass
the revised test suite? If not, correct it so that it does.
c. Run this test suite on five of the variants mentioned in Exercise
2 that you have either not tested or that have passed all tests so
far. How many pass the new test suite?
Exercise 7: Symmetric Tests
We've tested for each of the three kinds of triangles, but we've
only one test for each. What if the programmer mistakenly forgets to
deal with the different orderings of parameters? We should make sure
that the implementation works for each.
a. Add tests to the test suite for classify-triangle to
ensure that classify-triangle correctly identifies the
three kinds of triangles, not matter what the ordering. In
particular, make sure that you test for the three variants of
isosceles triangles.
(test! (classify-triangle 2 2 3) "isosceles")
(test! (classify-triangle 2 3 2) "isosceles")
(test! (classify-triangle 3 2 2) "isosceles")
b. Are there other tests in which the ordering might matter? (Hint:
Think about some of the tests for errors.)
c. Does your version of classify-triangle pass
the revised test suite? If not, correct it so that it does.
d. Run this test suite on five of the variants mentioned in problem
2 that you have either not tested or that have passed all tests so
far. How many pass the new test suite?
Exercise 8: Testing Large Sides
We now might consider the range of side values for
which classify-triangle should be tested.
a. Add tests that ensure that classify-triangle
works for very large numbers (say, numbers greater than 10 billion).
b. Does your version of classify-triangle pass
the revised test suite? If not, correct it so that it does.
c. Run this test suite on five of the variants mentioned in problem
2 that you have either not tested or that have passed all tests so
far. How many pass the new test suite?
a. Add any other tests you conceive of.
b. Be prepared to discuss those tests in class.
c. Does your version of classify-triangle pass
the revised test suite? If not, correct it so that it does.
d. Run these tests on any variants mentioned in problem 2 that you
have not yet tested or that have passed all the tests up through
exercise 9. How many pass the tests?
