1 00:00:00,990 --> 00:00:06,510 OK, one more thing I want to turn our attention to, and it is a very important component and one that 2 00:00:06,510 --> 00:00:12,900 gets ignored far too often by developers, especially new developers, and that is testing when we write 3 00:00:12,900 --> 00:00:17,710 code, we want to write tests to ensure that our code actually does what it's supposed to do. 4 00:00:18,120 --> 00:00:20,660 Fortunately, go makes this remarkably easy. 5 00:00:21,240 --> 00:00:23,070 So, first of all, we need something to test. 6 00:00:24,000 --> 00:00:30,300 So what I'm going to do, I have a new project here with one file named Echo, and inside of that I 7 00:00:30,300 --> 00:00:31,920 have an empty main function. 8 00:00:31,920 --> 00:00:34,280 And as you have to have, I'm going to create a new function. 9 00:00:34,560 --> 00:00:41,310 I'm going to call this function divide and it's going to take two parameters, X and Y, not very original 10 00:00:41,310 --> 00:00:46,440 variable names, but they'll do the trick and they're going to be off type float 32 and it's going to 11 00:00:46,440 --> 00:00:48,420 return one of two things. 12 00:00:48,420 --> 00:00:49,920 Well, Ash is going to return to things. 13 00:00:50,040 --> 00:00:56,850 It's going to return a float 32, which will be the result of our division and an error which will have 14 00:00:56,850 --> 00:01:00,440 an error if there is an error or it will be nil if there is no error. 15 00:01:00,990 --> 00:01:03,990 So it takes two parameters and it returns to things. 16 00:01:04,560 --> 00:01:08,090 Now, the very first thing we need, of course, is a place to store a result. 17 00:01:08,100 --> 00:01:15,570 So I'll find a new variable var and I'll just call a result and it's a type float 32 and then we can 18 00:01:15,570 --> 00:01:16,260 do our division. 19 00:01:16,290 --> 00:01:24,240 Our division is result equals X divided by Y and then I need to return our result and an error if we 20 00:01:24,240 --> 00:01:24,720 have one. 21 00:01:24,900 --> 00:01:31,870 Now sadly this will never throw an error that I can catch, so I need to check for something. 22 00:01:31,890 --> 00:01:33,750 Now what situations are there. 23 00:01:34,440 --> 00:01:39,440 We're dividing one float by another or one number by another will result in an error. 24 00:01:39,960 --> 00:01:44,670 And if you took math at all at any point in the past, you'll know that division by zero is generally 25 00:01:44,670 --> 00:01:45,480 frowned upon. 26 00:01:46,410 --> 00:01:49,460 You can't divide something by zero or you get an undefined result. 27 00:01:49,470 --> 00:01:50,250 So that's our error. 28 00:01:50,490 --> 00:01:56,940 So I can just check to say if y which is what I'm dividing by right here, if that's equal to zero, 29 00:01:57,090 --> 00:01:58,360 then return an error. 30 00:01:58,380 --> 00:02:00,180 So I will return and I'll return. 31 00:02:00,190 --> 00:02:01,840 I have to return to things. 32 00:02:01,870 --> 00:02:06,930 I'll return result which is set to zero right now because I've just initialize that, not done anything 33 00:02:06,930 --> 00:02:09,870 with it and then I'll just generate my own error. 34 00:02:10,140 --> 00:02:15,960 And it's as simple as this errors knew and then I will put in my error. 35 00:02:15,960 --> 00:02:19,050 Message cannot divide by zero. 36 00:02:19,410 --> 00:02:19,780 That's it. 37 00:02:20,490 --> 00:02:23,820 So now I can return nil down here because there is no air. 38 00:02:24,150 --> 00:02:25,050 So let's go through this. 39 00:02:25,050 --> 00:02:26,490 Here's a function called divide. 40 00:02:26,970 --> 00:02:30,270 I initialize a variable type happens to be float 32. 41 00:02:30,570 --> 00:02:36,030 I checked to make sure what I'm dividing by our deviser y is not zero. 42 00:02:36,030 --> 00:02:41,100 If it is equal to zero, return the result, which is zero because I haven't done anything with it and 43 00:02:41,100 --> 00:02:42,780 an error that I've created myself. 44 00:02:43,170 --> 00:02:48,870 Otherwise, if Y is not equal to zero to the division, return the result and return nil for an error 45 00:02:49,050 --> 00:02:50,310 and appear in the main function. 46 00:02:50,670 --> 00:02:57,480 All I have to do is call it so I'll say result and error, which is an error there. 47 00:02:57,480 --> 00:03:04,950 Assign the value of divide and I'll just do one hundred divided by ten and they'll check for my error. 48 00:03:05,340 --> 00:03:08,580 If error is not equal to nil, what should I do. 49 00:03:09,180 --> 00:03:13,020 I should just say, well, log print line error and return. 50 00:03:13,170 --> 00:03:13,980 Don't do anything else. 51 00:03:14,010 --> 00:03:14,970 Stop at that point. 52 00:03:15,150 --> 00:03:17,040 Otherwise, what am I going to do. 53 00:03:17,190 --> 00:03:22,800 Log print line result of division is and then my result. 54 00:03:23,730 --> 00:03:24,090 All right. 55 00:03:24,090 --> 00:03:25,320 So I can run this program. 56 00:03:25,770 --> 00:03:27,270 Go run. 57 00:03:27,420 --> 00:03:29,400 May not go and it should work. 58 00:03:31,410 --> 00:03:32,650 Result of division is 10. 59 00:03:32,730 --> 00:03:33,270 Perfect. 60 00:03:33,490 --> 00:03:39,810 OK, now what if I try to divide by zero, just changes to zero, clear the screen. 61 00:03:42,100 --> 00:03:44,780 And run it again cannot divide by zero. 62 00:03:44,800 --> 00:03:52,720 That works great, but the entire purpose of this exercise is not to learn how to divide because you 63 00:03:52,720 --> 00:03:53,880 probably already know how to do that. 64 00:03:53,980 --> 00:03:55,100 It's to write tests. 65 00:03:55,120 --> 00:03:59,110 So here's how you write tests and go in go the tests. 66 00:03:59,350 --> 00:04:03,130 The tests themselves live right beside the coalition trying to test. 67 00:04:03,310 --> 00:04:05,100 So I have one file, mango. 68 00:04:05,440 --> 00:04:11,190 I'll now create another file and it has to have a specific kind of name and fortunately is pretty easy. 69 00:04:11,800 --> 00:04:21,430 So when I create my file, I will call it new go file, main underscore test or go, which means these 70 00:04:21,430 --> 00:04:23,540 are the tests for mango. 71 00:04:24,040 --> 00:04:26,510 So it has to end with underscore test go. 72 00:04:28,240 --> 00:04:29,810 So how do we write tests? 73 00:04:29,830 --> 00:04:35,410 Well, I'm going to show you two ways, one way, which is kind of manual and slow and one another way 74 00:04:35,440 --> 00:04:36,550 which is way more efficient. 75 00:04:36,640 --> 00:04:41,680 But we'll do the easy ones first, the manual ones to write, to write a test and go. 76 00:04:41,680 --> 00:04:42,400 It's just a function. 77 00:04:42,640 --> 00:04:45,910 And you have to give the function a name and it has to start with the word test. 78 00:04:45,910 --> 00:04:47,680 Otherwise it's going to get ignored. 79 00:04:47,680 --> 00:04:51,360 And I'm going to test divide because I have a function called write. 80 00:04:51,400 --> 00:04:52,450 So I'm going to do that. 81 00:04:52,900 --> 00:04:58,930 And it takes this for argument's T is the conventional name that you're going to use for this variable. 82 00:04:59,260 --> 00:05:03,040 And it's a pointer to testing Dorte, which is a built in package. 83 00:05:03,430 --> 00:05:05,310 So you see that an important testing for me. 84 00:05:05,680 --> 00:05:10,480 Now, I write my tests and all I do is I need to get the result in this case. 85 00:05:10,480 --> 00:05:13,240 I don't care what the result is, I'm going to call that function. 86 00:05:13,930 --> 00:05:20,500 I'm going to check for an error and I'll divide, oh, let's say ten point zero and one point zero. 87 00:05:21,070 --> 00:05:25,540 OK, if error is not equal to nil, then what do I do? 88 00:05:25,930 --> 00:05:28,450 I throw an error, but I don't throw a standard error. 89 00:05:28,450 --> 00:05:29,500 I throw a testing error. 90 00:05:29,650 --> 00:05:31,510 T dot error. 91 00:05:32,230 --> 00:05:36,430 Got an error when we should not have. 92 00:05:38,260 --> 00:05:42,040 So I'm checking for air, but I'm not checking for errors in my programming code. 93 00:05:42,280 --> 00:05:45,330 I'm checking to see whether an error is actually thrown. 94 00:05:45,340 --> 00:05:51,900 So in this case, when I divide ten by one, that's absolutely valid and I should not get an error. 95 00:05:52,090 --> 00:05:57,190 So all I'm running here is a test to say if I divide ten by one, I should not get an error. 96 00:05:57,200 --> 00:05:59,470 If I do, then fail this test. 97 00:05:59,500 --> 00:06:00,280 So let's run this. 98 00:06:00,280 --> 00:06:02,740 And here's how you run tests and go go test. 99 00:06:03,610 --> 00:06:05,470 That's pretty easy and pass. 100 00:06:05,470 --> 00:06:08,260 OK, and I can actually do a little bit more detail. 101 00:06:08,260 --> 00:06:16,030 Go test Dash V for verbose and it says I'm running testified, I pass testified and it told me how long 102 00:06:16,030 --> 00:06:18,190 it took to run all the questions around all the tests. 103 00:06:18,730 --> 00:06:20,070 Now that's one test. 104 00:06:20,080 --> 00:06:26,140 Let's try copying this and I'm going to copy and paste it and give it a new name test, bad divide, 105 00:06:26,140 --> 00:06:30,040 I'll call it this time, meaning I'm testing for bad division. 106 00:06:30,040 --> 00:06:34,270 And this time I'm going to say divide ten by zero. 107 00:06:34,990 --> 00:06:38,950 In this case, what should happen if error is equal to nil? 108 00:06:38,980 --> 00:06:48,270 If it doesn't throw an error we say did not get an error when we should have and again, think it through. 109 00:06:48,790 --> 00:06:55,330 If I divide ten by zero, it should generate that error that we wrote in our function and return zero 110 00:06:55,330 --> 00:06:56,020 and an error. 111 00:06:56,410 --> 00:06:58,390 So error should not be equal to nil. 112 00:06:58,600 --> 00:07:06,190 If error is equal to nil, then I failed the test so we can now run the test again, go test and again 113 00:07:06,190 --> 00:07:07,600 it should pass and they both pass. 114 00:07:08,020 --> 00:07:14,350 Now, the problem here, of course, is what if I really want to test my division function thoroughly? 115 00:07:14,770 --> 00:07:19,720 I'm going to wind up writing one function for every one of these tests, and that's really, really 116 00:07:19,720 --> 00:07:20,410 inefficient. 117 00:07:20,770 --> 00:07:26,830 So instead, let's run what's called a table test and we'll do this, first of all, by showing what 118 00:07:26,830 --> 00:07:28,660 kind of data I want to test. 119 00:07:28,660 --> 00:07:33,880 So right at the top of my program, right after my input statement, I'm going to write a variable tests 120 00:07:34,210 --> 00:07:39,430 and it's going to be equal to a slice of stroke's slice of strokes. 121 00:07:40,210 --> 00:07:42,700 And inside of that, I have to define the struct. 122 00:07:42,970 --> 00:07:46,120 So first of all, I want to give my testimony, which is just a string. 123 00:07:47,050 --> 00:07:52,040 Then I'm going to give my name, my dividend, my first number that I'm passing, which is a thirty 124 00:07:52,090 --> 00:07:53,890 two dividend. 125 00:07:53,890 --> 00:08:01,510 I better still write and then the deviser, but I'm dividing by which is again a float thirty two. 126 00:08:02,620 --> 00:08:03,520 Is that enough. 127 00:08:03,530 --> 00:08:04,540 No it's not. 128 00:08:04,540 --> 00:08:09,280 I want to also include what do I expect to get from the results of this division. 129 00:08:09,280 --> 00:08:11,980 So I'll call it expected and it's a float. 130 00:08:11,980 --> 00:08:16,300 Thirty two and finally I'm going to put in one more variable. 131 00:08:16,300 --> 00:08:18,340 Is an error expected. 132 00:08:18,340 --> 00:08:21,160 So is error which is a boolean true or false. 133 00:08:21,310 --> 00:08:24,600 OK then that defines my struct. 134 00:08:24,610 --> 00:08:30,310 Now it's populated with some test data and what we're going to have is every entry in this slice will 135 00:08:30,310 --> 00:08:32,140 be a test that I run once. 136 00:08:32,500 --> 00:08:37,900 So first of all, I'm going to call my test is valid data and that name can be whatever you want. 137 00:08:37,900 --> 00:08:39,700 But my test is testing with valid data. 138 00:08:39,940 --> 00:08:45,790 I'll pass in one hundred point zero as my first number, ten point zero is my second number and ten 139 00:08:45,790 --> 00:08:47,470 point zero is the expected result. 140 00:08:47,680 --> 00:08:50,890 And this should not throw an error. 141 00:08:51,190 --> 00:08:54,280 So each of these values corresponds to each of these in order. 142 00:08:54,520 --> 00:08:57,820 So I'm having a test named for all the data I want to divide. 143 00:08:57,820 --> 00:08:58,840 One hundred by ten. 144 00:08:58,840 --> 00:09:01,720 I expect to get ten as a result and I expect no error. 145 00:09:02,050 --> 00:09:09,220 Now let's duplicate that line and call it invalid data hundred divided by zero and I can put zero point 146 00:09:09,220 --> 00:09:13,330 zero because it's a float and the result I'm expecting is zero. 147 00:09:15,110 --> 00:09:19,320 And am I expecting an error? 148 00:09:19,340 --> 00:09:23,330 Yes, if I try to divide by zero, then I should get an error. 149 00:09:23,630 --> 00:09:25,220 OK, let's just go with those two for now. 150 00:09:25,340 --> 00:09:28,550 These two effectively duplicate the two tests I've written already. 151 00:09:29,060 --> 00:09:29,960 I'll leave those there. 152 00:09:30,440 --> 00:09:33,170 But now I want to write a new function func. 153 00:09:33,170 --> 00:09:39,710 I'll call it test division and there's no tie and function test division. 154 00:09:40,940 --> 00:09:45,860 And it is again a Ts type testing T. 155 00:09:48,360 --> 00:09:50,820 And I put its parentheses there as curly brackets. 156 00:09:51,420 --> 00:09:55,490 Now I'm going to range over my test variable so we can know how to do that. 157 00:09:55,500 --> 00:09:57,830 We've already done that for I ignore the first one. 158 00:09:57,840 --> 00:10:03,360 I don't care what the index is for each test and I'll call it teet, which is pretty common when you're 159 00:10:03,360 --> 00:10:06,900 changing over tests equals range tests. 160 00:10:08,070 --> 00:10:10,530 And what do I want to do inside of that test? 161 00:10:10,560 --> 00:10:13,100 Well, first of all, let's just call that function. 162 00:10:13,110 --> 00:10:17,330 Got what am I getting from the function error? 163 00:10:18,240 --> 00:10:22,410 If there's an error, populate that variable, otherwise leave it is nil and call the function divide. 164 00:10:23,610 --> 00:10:27,870 And I'm going to call it the passing the two arguments right from this slice. 165 00:10:27,990 --> 00:10:38,760 So I address those by going to dot dividend t t dot divisor and then I actually run my checks. 166 00:10:38,910 --> 00:10:41,070 So first of all, what am I checking for. 167 00:10:41,490 --> 00:10:44,010 Well let's check, first of all to see if it should have an error. 168 00:10:44,040 --> 00:10:45,920 If T t is error. 169 00:10:46,080 --> 00:10:50,910 In other words, if this test is supposed to throw an error, then check to see if the error is now 170 00:10:50,910 --> 00:10:53,070 because of the error is no, I failed the test. 171 00:10:53,370 --> 00:10:56,940 If error is equal to nil, then fail the tests. 172 00:10:56,940 --> 00:11:05,360 I can put T to error expected and error, but did not get one. 173 00:11:06,390 --> 00:11:07,440 So that's the first check. 174 00:11:09,780 --> 00:11:14,970 So a second case would be if the error is not equal, if there is equal to. 175 00:11:15,510 --> 00:11:17,660 So that would be an opt out. 176 00:11:19,260 --> 00:11:27,060 And now I can check to see if error is not equal to nil, then I throw another Teda error. 177 00:11:28,470 --> 00:11:36,150 And this one is did not expect an error, but got one. 178 00:11:38,690 --> 00:11:44,390 And then to confront the threat, which is er error, I could just put air there, but you can also 179 00:11:44,390 --> 00:11:46,660 call the method on that which will give it as a strength. 180 00:11:47,640 --> 00:11:49,080 OK, so that's our first case. 181 00:11:49,520 --> 00:11:53,810 And then finally, we need to check to see did we get what we expected to get. 182 00:11:53,960 --> 00:12:01,730 If God is not equal to TTD expected, then throw another Teege error. 183 00:12:01,940 --> 00:12:06,410 And this time I'll use Şeref because I'm going to put some placeholders in there. 184 00:12:06,890 --> 00:12:12,650 Expected percent F, but got percent F. 185 00:12:14,280 --> 00:12:20,850 And then I just populate those placeholders with expected and got so I expected to the expected and 186 00:12:20,850 --> 00:12:22,830 got there. 187 00:12:23,400 --> 00:12:25,480 All right, let's run this test and see what happens. 188 00:12:26,070 --> 00:12:27,180 Go test. 189 00:12:29,220 --> 00:12:38,490 And they all passed, and if I do go test you go test Daschle, you see, that is actually running those 190 00:12:38,490 --> 00:12:45,660 test runs test division twice because I have two values up here and then it runs the two manual ones. 191 00:12:45,690 --> 00:12:49,700 But I don't really need those anymore so I can get rid of them because I'm already testing them. 192 00:12:49,710 --> 00:12:55,320 And the great thing about this is if I want to run more tests on that, I just duplicate this and put 193 00:12:55,320 --> 00:12:56,280 some more values in here. 194 00:12:56,280 --> 00:13:02,370 So I'll put one where I expect certain results expected or expect five. 195 00:13:02,580 --> 00:13:03,520 How do I get five? 196 00:13:03,540 --> 00:13:09,780 Well, fifty divided by ten should give me five and now I can run those tests. 197 00:13:10,890 --> 00:13:11,670 And it works great. 198 00:13:11,700 --> 00:13:16,600 OK, let's take it here, expected an error, but did not get one fail test division, so. 199 00:13:16,650 --> 00:13:19,800 Oh yeah, down here I expect no air false. 200 00:13:20,360 --> 00:13:21,330 See, that's how they work. 201 00:13:22,870 --> 00:13:29,590 So clear the screen, run this again and away it goes, if I want to put another one in there, say 202 00:13:29,920 --> 00:13:34,630 expect fractioned so we're not going to do a whole division this time. 203 00:13:34,630 --> 00:13:39,790 So we'll do minus one divided by minus 777. 204 00:13:40,100 --> 00:13:41,290 And what does that give us? 205 00:13:41,320 --> 00:13:42,940 Well, I already did this on a calculator. 206 00:13:42,940 --> 00:13:47,230 It gives a zero point zero zero one two eight seven zero zero one three. 207 00:13:47,620 --> 00:13:49,750 And if I typed that right, this test should pass. 208 00:13:52,020 --> 00:13:56,640 And it passed, and that's all there is to testing now, one more thing about this, we can actually 209 00:13:56,640 --> 00:14:04,240 check our test coverage by going go test cover and it will tell me that I actually have in my testing 210 00:14:04,240 --> 00:14:10,590 course here, I have 50 percent of the statements are covered and we can even get better than that. 211 00:14:11,310 --> 00:14:17,810 And we can do so by running this command, which I'm going to paste in go test dashkova profile equals 212 00:14:17,820 --> 00:14:21,480 coverage out, which will spitfire's up here called coverage out. 213 00:14:21,840 --> 00:14:26,670 And then if that is successful, run, go to cover HTML equals coverage. 214 00:14:26,880 --> 00:14:27,660 And if I run that. 215 00:14:29,670 --> 00:14:35,970 It actually fires up my Web browser for me and shows me what's covered in green and what's not covered 216 00:14:35,970 --> 00:14:36,550 in red. 217 00:14:37,230 --> 00:14:40,770 Now, realistically speaking, a 50 percent test coverage is not great. 218 00:14:41,070 --> 00:14:47,490 But the reality is we're going to, throughout the course of this course, make our main functions as 219 00:14:47,490 --> 00:14:50,700 dumb as we possibly can and not bother testing them. 220 00:14:50,700 --> 00:14:55,890 So we're going to do as little in here as we possibly can instead of doing a lot within our main function. 221 00:14:55,890 --> 00:15:02,580 As time goes on, we'll begin to pass all of our actions off to functions and we'll test those functions. 222 00:15:02,580 --> 00:15:04,430 And we just won't bother to test our main function. 223 00:15:04,440 --> 00:15:09,270 And we'll get pretty, pretty good course test coverage as we go through this course. 224 00:15:09,420 --> 00:15:09,750 All right. 225 00:15:09,750 --> 00:15:10,560 That's it for testing. 226 00:15:10,560 --> 00:15:15,120 We'll see lots more of examples of this as we begin writing more sophisticated code.