Agile Development & Companies

Transcription

1 Agile Development & Companies Harvard Business Review: Why the lean start-up changes everything Agile development applied to entire business of start-ups Iterate! Simplest possible prototype! Image: leadnet.org

2 Vaughn Betz ECE 297 Testing

3 Testing Philosophy If you didn t test it, it doesn t work Assume all code broken until proven otherwise Look at what the program does not what it is supposed to do Scientist: you are testing hypotheses about program Think of every case your program should handle cover them all

4 Testing Time Develop tests as or before you code Test-driven development Prototype Refine Test & Evaluate

5 Test-Driven Development The tests are the detailed specification And now can be executed, not just read Less specification document More tests

6 Types of Tests End to End Tests End-to-end (system) tests Test entire system (like end user would) Hard to debug a failure problem could be anywhere! Fragile: often test some exact user input would produce some exact output text / file Unit Tests Unit Tests Test small pieces of system (single classes / functions) Much easier to debug a failure start with that class / function Don t check user interface (I/O): check API / class does what it should with code (testfixture)

7 Types of Tests End to End Tests Integration Tests Integration Tests Bigger unit tests Work the same way But now test multiple classes / bigger functionality Moderate difficulty to debug Unit Tests

8 You will re-test often Testing Automation Every time you change the program How to speed up? System tests: save in files Use file redirection prog.exe < in.txt > out.txt diff out.txt out_good.txt // matched known good result? Less fragile Write validity checker instead of checking exact output match Write scripts to run all tests and check results

9 Want: Unit Tests To test individual classes / functions How? Carefully chosen user input? Output... No! struct Point { float x; float y; t_point& operator*=(float rhs);...

10 Unit Tests Write new code To put class in right state To directly send it some input / make some calls To immediately check the responses Test driver

11 Unit Tests struct Point { float x; float y; t_point& operator*=(float rhs);... test_main.cpp int main () { int error = 0; error += test1();... // Lots more tests mycode.cpp tester.cpp int test1 () { Point testme (1, 2); testme *= 3; if (testme!= Point (3, 6)) { cout << uh oh << endl; return (1); return (0); g++ mycode.cpp main.cpp o prog.exe g++ mycode.cpp tester.cpp test_main.cpp o test.exe

12 Unit Test Frameworks Lots of repetitive code to create test drivers Set up the test Check if the test passed Run all the tests Output appropriate messages Collect statistics Unit Test Frameworks Useful macros (#defines) and functions to simplify coding We are using UnitTest++ Powerful, but easy to learn ECE 297 Unit Test Quick Start Guide TEST(..) or TESTFIXTURE ( ) CHECK(..) RunAllTests() Automatic Automatic

13 Overlapping tests good Test the Seams Your code + partner s code Both unit tested Make sure there s an integration test Therac-25

14 What tools? 1. Debugger Testing Tools Use to debug when a test fails Use to verify new code Step through it and watch execution 2.Memory checker Program seg faults? Program behaving very strangely? Maybe you are accessing memory you shouldn t be! Run valgrind

15 3. Code coverage MyCode.cpp Testing Tools Tools that can track what lines of your programs have executed over all your tests int somefunc (int input) { if (input == 0) return (3); else return (7); main.cpp int main () { int j = somefunc (8); // Wow I m bad at testing!

16 3. Code coverage Testing Tools Tools that can track what lines of your programs have executed over all your tests MyCode.cpp int somefunc (int input) { if (input == 0) return (3); else return (7); No test reaches this line. Code coverage: 6 out of 7 lines or 86% main.cpp int main () { int j = somefunc (8); // Wow I m bad at testing!

17 Google: Testing so Important, Tutorials in the Bathroom

18 Testing on the Toilet

19 Good Coding Style

20 1. Use White Space int sumvec (int vec[], int nelem) { int i, result = 0; for (i = 0; i < nelem; i++) { result += vec[i]; return (result); void nextfunc (int i) { int sumvec (int vec[], int nelem) { int i, result = 0; for (i = 0; i < nelem; i++) { result += vec[i]; return (result); void nextfunc (int i) { White space: show code organization Indent properly (3 or 4 spaces) per {. Leave blank lines between functions / key blocks

21 float di (float a, float b) { float val, d, x, x2, y; What does this do? d = 1.e-4; val = 0; for (x = a; x < b; x += d) { x2 = x + d; if (x2 > b) x2 = b; y = 0.5 * ((1. / x) + (1. / x2)); val += y * (x2 - x); return (val);

22 float definite_integral (float x_left, float x_right) { float integral, step_size, x1, x2, y_average; What does this do? step_size = 1.e-4; integral = 0; for (x1 = x_left; x1 < x_right; x1 += step_size) { x2 = x1 + step_size; if (x2 > x_right) x2 = x_right; y_average = 0.5 * ((1. / x1) + (1. / x2)); integral += y_average * (x2 x1); return (integral);

23 2. Descriptive Variable Names Use descriptive names Variables, functions, structs/types, get_file_name ( ); // Use _ to separate getfilename (); // Or use upper case to mark words Types: start with a capital letter Variables: start with lowercase class MyClass { MyClass onevar;

24 float definite_integral (float x_left, float x_right) { float integral, step_size, x1, x2, y_average; What does this do? step_size = 1.e-4; integral = 0; for (x1 = x_left; x1 < x_right; x1 += step_size) { x2 = x1 + step_size; if (x2 > x_right) x2 = x_right; y_average = 0.5 * ((1. / x1) + (1. / x2)); integral += y_average * (x2 x1); return (integral);

25 // Compute the definite integral of 1/x between x_left and x_right via the // trapezoidal method. Smaller values of step_size improve accuracy, but // increase computation time. Comment what whole function does float definite_integral_of_one_over_x (float x_left, float x_right) { float integral, step_size, x1, x2, y_average; step_size = 1e-4; integral = 0.; for (x1 = x_left; x1 < x_right; x1 += step_size) { x2 = x1 + step_size; if (x2 > x_right) // in case (x_right x_left) is not a multiple of step_size x2 = x_right; y_average = 0.5 * ((1. / x1) + (1. / x2)); // average of y(x1) and y(x2) integral += y_average * (x2 x1); return (integral); Comment any tricky bits of code

26 Comments: Usefulness? trans_sim.cpp /* Functions to simulate transistors. * We model transistors as nonlinear elements, * by looking up the source-drain current for each V */ StudentRecord.h /* Main data structure used to store all information * about a U of T student. Linked list. */ struct StudentRecord { int nclassescurrent; // Number of classes enrolled in. int nclassescomplete; // Number of completed classes, // not including currently enrolled ones StudentRecord *next; // Pointer to next (linked list) record program.cpp // Compute the sum of the array, over all its elements int sum = 0; for (int i = 0; i < nelem; i++) sum += array[i];

27 3. High-Level Comments Most important comments: give the big picture Documentation should be in the comments Not a separate document will get out of date 1. Top of files // Functions to simulate transistors. We proceed in 6 stages 2. Class / data structure definitions Understand the data can understand the program! 3. Start of functions 4. Tricky code Not very useful comments: Translate C++ to English Most important Least important

28 Thoughts on This Code? int checkweights (int weights[20]) { for (int i = 0; i < 20; i++) { if (weights[i] < 0) return (-1); if (weights[i] == 0) return (1); return (0); 1. Using a magic number : 20 Change array size: must find and change all 20 s 2. Returning magic numbers: -1, 0, 1 Must read code carefully to see what each means

29 4. Use Named Constants const int NUM_WEIGHTS = 20; // 1. Constant variable #define WEIGHT_ZERO 0 // 2. Pre-processor constant enum WtReturn {HAS_NEG = -1, HAS_ZERO = 0, ALL_POS = 1; // 3. make an enumeration (list) of int constants int checkweights (int weights[num_weights]) { for (int i = 0; i < NUM_WEIGHTS; i++) { if (weights[i] < 0) return (HAS_NEG); if (weights[i] == 0) return (HAS_ZERO); return (ALL_POS); Three ways to make constants use any way you like Name: ALL CAPITALS (convention)