ToLower() is not required for path, as GetFiles considers it as case insensitive.

resolved

Can you also verify that the about_testCase.help.txt is one of the files that is returned by Get-Help?

resolved by only get the specified files start with about_testcase*

Get-Help can get help content from other paths under PSModulePath. So if there are other about help topics not under $PSHome, the counts would not match.

resolved

looks like a formatting mistake here

The formatting is fixed. It shows normal under IDE, I have to delete and re tab to fix it.

why the formatting change?

resolved

Since this matching is infrequent, you should use an interpreted regex instead of a compiled one

https://msdn.microsoft.com/en-us/library/gg578045(v=vs.110).aspx

You can also use RegEx.IsMatch(filePath, regexPattern). This avoids instantiating the an RegEx object and RegEx engine caches the compiled version for reuse.

resolved

This test case doesn't cover the code change, you explicitly handle *, ?, and .

Seems like you should also have a test case with multiple wildcards

resolved.

RegEx.Escape(pattern) should be used first, before any replaces.

This actually should not be used. RegEx.Escape will also escape the '*' and '?' which we want them as normal character to replace later.

You can also use RegEx.IsMatch(filePath, regexPattern). This avoids instantiating the an RegEx object and RegEx engine caches the compiled version for reuse.

Can all this code be replaced by:

return Directory.GetFiles(path).Where(f => Regex.IsMatch(f, regExPattern.ToString())).ToArray();

return Directory.GetFiles(path).Where(f => Regex.IsMatch(f, regExPattern.ToString())).ToArray(); is not implementing the logic of string which is not using a pattern

Extra space after {

resolved

Typos:
Tranvis -> Travis
specified -> specific

resolved

The if block can be replace by the following. If it already exists, it is not modified.

$null = New-Item -ItemType Directory -Path $helpFolderPath -Force

resolved

For all the Shoulds, use Be or BeExactly. Match uses regular expression comparison. It is not required here.

resolved

Ideally, each It should have only one Should. This ensures that if the first should fails, the rest are not ignored. Take a look at: http://www.powershellmagazine.com/2015/06/04/pester-triangulation-and-reusing-test-cases/
You can pass the values for Get-Help as testcases and values for Should as expected values. Using testcases parameter of It also allows you to give better names for each variation.

Agree with @adityapatwardhan, this is a good example to use the -TestCases parameter of Pester. Look at other test code in this repo as a sample.

resolved with triangulation format. a good way !

unless the testcases are used in other tests, I would prefer to have these inline to the It statement as it makes it easier to associate the two

A good example of using test cases would be:

resolved

A good example of using test cases would be:

Can these be done in beforeall and cleanup in afterall?

Don't use Invoke-Expression instead use splatting instead. Look at: 28ec9a3

In that case (Get-Help about_testCase*).Count would needs to be explicitly written in the test case one more time. If u think this is better than invoke-expression i will update later.

After talking to Jim, in general Invoke-Expression is not a best practice. An alternative approach would be to make the command as script block. So the test would look like:

$testcases = @( 
                  @{command = {Get-Help about_testCas?1}; testname = "test ? pattern"; result = "about_test1"} 
                  @{command = {Get-Help about_testCase.?}; testname = "test ? pattern with dot"; result = "about_test2"} 
                  @{command = {(Get-Help about_testCase*).Count}; testname = "test * pattern"; result = "2"} 
                  @{command = {Get-Help about_testCas?.2*}; testname = "test ?, * pattern with dot"; result = "about_test2"} 
               ) 

And replace Invoke-Expression with

$command.Invoke() | Should be $result

This should be marked as Pending on Non-Windows and not skipped. So we can revisit later.

resolved

Typo: Tranvis -> Travis.

resolved

$helpFolderPath does not seem to be cleaned up? Maybe you can just delete $helpFolderPath recursively.

$helpFolderPath is an existed folder contains other help files.

After talking to Jim, in general Invoke-Expression is not a best practice. An alternative approach would be to make the command as script block. So the test would look like:

$testcases = @( 
                  @{command = {Get-Help about_testCas?1}; testname = "test ? pattern"; result = "about_test1"} 
                  @{command = {Get-Help about_testCase.?}; testname = "test ? pattern with dot"; result = "about_test2"} 
                  @{command = {(Get-Help about_testCase*).Count}; testname = "test * pattern"; result = "2"} 
                  @{command = {Get-Help about_testCas?.2*}; testname = "test ?, * pattern with dot"; result = "about_test2"} 
               ) 

And replace Invoke-Expression with

$command.Invoke() | Should be $result

Why are we using regular expression matching instead of wildcard matching?

FWIW - wildcard matching already converts the wildcard to a regex - so this code is probably doing something similar but subtly different.

I agree. We basically need to implementation Directory.GetFiles(path, pattern); in a case-insensitive way, and the code at https://github.com/PowerShell/PowerShell/blob/master/src/System.Management.Automation/engine/CommandCompletion/CompletionCompleters.cs#L5961 is doing the same thing.

#4053 is opened for this.
Never mind, it's a duplicate of #3967