adding pester tests

images/win/scripts/Tests/Shell.Tests.ps1

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+Describe "Shell" {
+    $shellTestCases = @(
+        @{Name = "C:\shells\bash.exe"; Target = "C:\msys64\usr\bin\bash.exe"},
+        @{Name = "C:\shells\sh.exe"; Target = "C:\msys64\usr\bin\sh.exe"},
+        @{Name = "C:\shells\winbash.exe"; Target = "$env:SystemRoot\System32\bash.exe"},
+        @{Name = "C:\shells\git4bash.exe"; Target = "$env:ProgramFiles\Git\bin\bash.exe"},
+        @{Name = "C:\shells\msys2.exe"; Target = "C:\msys64\usr\bin\bash.exe"}
+    )
+
+    $pathTestCases = @(
+        @{Path = "C:\shells"},
+        @{Path = "C:\msys64\mingw64\bin"},
+        @{Path = "C:\msys64\usr\bin"}
+    )
+
+    It "Default bash.exe from MSYS2" {
+        (Get-Command bash).Path | Should -BeExactly "C:\shells\bash.exe"
+    }
+
+    It "Default sh.exe from MSYS2" {
+        (Get-Command sh).Path | Should -BeExactly "C:\shells\sh.exe"
+    }
+
+    It "Folder C:\shells exists" {
+        "C:\shells" | Should -Exist
+    }
+
+    It "C:\Windows\System32 before C:\msys64\mingw64\bin and C:\msys64\usr\bin" {
+        $path = $env:Path.Split(";").ToLower()
+        $indexOfSystem32 = $path.IndexOf("c:\windows\system32")
+
+        $path.IndexOf("c:\msys64\mingw64\bin") | Should -BeGreaterThan $indexOfSystem32
+        $path.IndexOf("c:\msys64\usr\bin") | Should -BeGreaterThan $indexOfSystem32
+    }
+
+    It "<Name> target to <Target>" -TestCases $shellTestCases {
+        (Get-Item $Name).Target | Should -BeExactly $Target
+    }
+
+    It "<Path> is in PATH" -TestCases $pathTestCases {
+        $env:Path.Split(";") | Should -Contain $Path
+    }
+}