net自动化测试之道API测试-用空串测试

Dealing with Empty String Input Arguments

参数为空串时的处理方法

Problem

You want to test empty string arguments passedto API methods under test.

问题

如何测试将空串传给被测方法？

Design

Use a special string token to represent anempty string in your test case file and then add

branching logic to your test harness thatpasses a true empty string argument to the API

method under test.

设计

在测试用例文件中，用特殊的标记字符串代表空串，然后在测试套件中增加逻辑处理传递真正的空串给被测方法。

 解决方案

创建如下测试用例：

0001:SubString:put:computer:true

0002:SubString:xyz:computer:false

0003:SubString:emptystring:computer:true

在测试套件中增加特殊的逻辑处理有“emptystring”标记的测试用例：

tokens=line.Split(':');

if(tokens[2]=="emptystring")//specialinput

arg1="";

else

arg1=tokens[2];

boolactual=StringLib.Methods.SubString(arg1,tokens[3]);

if(actual==bool.Parse(tokens[4]))

Console.WriteLine("Pass");

else

Console.WriteLine("*FAIL*");

 

Comments

When testing API methods that accept stringarguments,you should always test for empty

strings.One way to deal with this is tostore a special string token such as“emptystring”in

your test case data file and then branchyour test case logic when that token is read.Suppose,

for example,you are testing a customStringLib library containing a custom SubString()

method that accepts two string argumentsand returns true if the first argument is contained

within the second argument.By design,thecustom SubString()method returns true if an

empty string is passed to its firstparameter.

Unlike null input,it is possible toindirectly store empty string input in a test case data

file.For example,the test case data string

0003:SubString::computer:true

when parsed byString.Split()into a string array named tokens will store an empty string

into tokens[2]becauseof the two consecutive colon characters.However,in general,it’s

much better to store a special string tokenbecause it makes your test case data easier to read

and validate programmatically.

The technique of embedding special stringtokens in your test case data file to deal with

empty string input can be used to test forother unusual input too.For example,suppose you

are testing a method that accepts acharacter input argument.You will want to test for control

characters such as<CR>and<LF>,andASCII vs.Unicode characters.You can store strings like

“<cr>”,“<lf>”,and“\u0041”in your test case data and then add special logic to your harness

to deal with them:

char input;

if(tokens[2]=="<CR>")//specialinput

input='\x000d';

else

input=char.Parse(tokens[2]);

 

If you have a lot of special tokens in yourtest case data file as is often the case,you can keep

your harness code cleaner and more scalableby writing a helper method Map(),which converts

the input value read from the test casedata file into the appropriate value.For example,you

could write:

private static charMap(string token)

{

if(token=="<CR>")

return'\x000d';

elseif(token=="<LF>")

return'\x000a';

//etc.

else

return char.Parse(token);

}

and then use it in your harness like this:

char input=Map(tokens[2]);

注解

当测试接受字符串参数的API方法的时候，我们应该总是会用空串去测试。一种方式是在测试用例文件中存储特殊的字符串标记例如“emptystring”，然后当改标记被读取的时候加以处理。假设我们正在测试一个叫StringLib的类，该类包含一个叫SubString的方法接收两个字符串参数，并且如果第二个参数包括第一个参数则返回true。通过设计，SubString方法的第一个参数是空串的时候返回true。

不像将null输入那样，在测试用例文件中可能不直接存储特殊标记表示空串。例如：

0003:SubString::computer:true

当使用String.Split()分解测试用例的时候，tokens字符串数组将空串存储在tokens[2]中，因为有两个连续的冒号。但是存储特殊字符串标记更好，因为这样我们的测试用例更容易读和使用程序验证。

在测试用例文件中签入特殊的字符串标记处理空串输入的技巧同样可以用于输入是其他特殊字符的情形。例如，假设我们测试一个接收字符输入的方法。我们想用控制字符如<CR>、<LF>、ASCII码、和Unicode字符。我们的测试用例可以用这些字符“<cr>”,“<lf>”,和 “\u0041”表示，然后在测试套件中的特殊逻辑中处理：

char input;

if(tokens[2]=="<CR>")//specialinput

input='\x000d';

else

input=char.Parse(tokens[2]);

如果我们的测试用例文件中的特殊标记像测试用例那样多，可以通过写一个Map()辅助方法使我们的测试套件的代码简洁并可扩展，该方法将从测试用例文件中读取的输入转换为方法需要的值。例如：

private static char Map(string token)

{

if(token=="<CR>")

return'\x000d';

else if(token=="<LF>")

return'\x000a';

//etc.

else

return char.Parse(token);

}

然后我们在测试套件中可以这样用：

char input=Map(tokens[2]);