Testing Basics

Expected and Actual

Separating expected and actual values makes failures easier to read.

expected value The expected value is what the test says should happen.

Expected and Actual

input
expected_actual.pl
Replay: real traced execution (multi-file project)
use strict;
use warnings;

sub add_two {
    my ($value) = @_;
    return $value + 2;
}

my $input = 4;
my $expected = 6;
my $actual = add_two($input);
my $status = $actual == $expected ? "pass" : "fail";

print "input=$input\n";
print "expected=$expected\n";
print "actual=$actual\n";
print "status=$status\n";

use strict;
use warnings;

sub add_two {
    my ($value) = @_;
    return $value + 2;
}

my $input = 1;
my $expected = 6;
my $actual = add_two($input);
my $status = $actual == $expected ? "pass" : "fail";

print "input=$input\n";
print "expected=$expected\n";
print "actual=$actual\n";
print "status=$status\n";

use strict;
use warnings;

sub add_two {
    my ($value) = @_;
    return $value + 2;
}

my $input = 5;
my $expected = 6;
my $actual = add_two($input);
my $status = $actual == $expected ? "pass" : "fail";

print "input=$input\n";
print "expected=$expected\n";
print "actual=$actual\n";
print "status=$status\n";

  1. $input ← 4, $expected ← 6

    9my $input→ 4 = 4; #@input=1, 510my $expected→ 6 = 6;11my $actual = add_two($input4);12my $status = $actual == $expected ? "pass" : "fail";

  2. $value ← 4

    4sub add_two {5    my ($value→ 4) = @_;6    return $value4 + 2;7}

  3. $actual ← 6, $status ← pass

    10my $expected = 6;11my $actual→ 6 = add_two($input4);12my $status→ pass = $actual6 == $expected6 ? "pass" : "fail";1314print "input=$input4\n";15print "expected=$expected6\n";16print "actual=$actual6\n";17print "status=$statuspass\n";
    outputinput=4
expected=6
actual=6
status=pass

  1. $input ← 1, $expected ← 6

    9my $input→ 1 = 1;10my $expected→ 6 = 6;11my $actual = add_two($input1);12my $status = $actual == $expected ? "pass" : "fail";

  2. $value ← 1

    4sub add_two {5    my ($value→ 1) = @_;6    return $value1 + 2;7}

  3. $actual ← 3, $status ← fail

    10my $expected = 6;11my $actual→ 3 = add_two($input1);12my $status→ fail = $actual3 == $expected6 ? "pass" : "fail";1314print "input=$input1\n";15print "expected=$expected6\n";16print "actual=$actual3\n";17print "status=$statusfail\n";
    outputinput=1
expected=6
actual=3
status=fail

  1. $input ← 5, $expected ← 6

    9my $input→ 5 = 5;10my $expected→ 6 = 6;11my $actual = add_two($input5);12my $status = $actual == $expected ? "pass" : "fail";

  2. $value ← 5

    4sub add_two {5    my ($value→ 5) = @_;6    return $value5 + 2;7}

  3. $actual ← 7, $status ← fail

    10my $expected = 6;11my $actual→ 7 = add_two($input5);12my $status→ fail = $actual7 == $expected6 ? "pass" : "fail";1314print "input=$input5\n";15print "expected=$expected6\n";16print "actual=$actual7\n";17print "status=$statusfail\n";
    outputinput=5
expected=6
actual=7
status=fail