Rework multi-source support test

tests/AnyPackage.Homebrew.Unit.Tests.ps1

@@ -132,29 +132,32 @@ Describe 'version tests' {
 	}
 }
 
-Describe "multi-source support" {
+Describe "error handling" {
 	BeforeAll {
-		$altSourceName = 'pyroscope-io/brew'
+		$altSource = 'pyroscope-io/brew'
 		$altSourceLocation = 'https://github.com/pyroscope-io/homebrew-brew'
 		$package = 'pyroscope'
-
+		
 		Unregister-PackageSource -Name $altSourceName -ErrorAction SilentlyContinue
 	}
 	AfterAll {
 		Unregister-PackageSource -Name $altSourceName -ErrorAction SilentlyContinue
 	}
 
-	It 'refuses to register a source with no location' {
-		Register-PackageSource -Name $altSourceName -Provider $providerShortName -ErrorAction SilentlyContinue | Where-Object {$_.Name -eq $altSourceName} | Should -BeNullOrEmpty
+	It 'refuses to find packages when the specified source does not exist' {
+		{Find-Package -Name $package -Source $altSource -ErrorAction Stop} | Should -Throw 'The specified source is not registered with the package provider.'
+	}
+	It 'refuses to install packages when the specified source does not exist' {
+		{Install-Package -Name $package -Source $altSource -ErrorAction Stop} | Should -Throw 'The specified source is not registered with the package provider.'
 	}
 	It 'registers an alternative package source' {
-		Register-PackageSource -Name $altSourceName -Location $altSourceLocation -Provider $providerShortName | Where-Object {$_.Name -eq $altSourceName} | Should -Not -BeNullOrEmpty
+		Register-PackageSource -Name $altSourceName -Location $altSourceLocation -Provider $providerShortName -PassThru | Where-Object {$_.Name -eq $altSourceName} | Should -Not -BeNullOrEmpty
 	}
 	It 'searches for and installs the latest version of a package from an alternate source' {
 		Find-Package -Name $package -Source $altSourceName | Install-Package -PassThru | Where-Object {$_.Name -contains $package} | Should -Not -BeNullOrEmpty
 	}
 	It 'unregisters an alternative package source' {
 		Unregister-PackageSource -Name $altSourceName
 		Get-PackageSource | Where-Object {$_.Name -eq $altSourceName} | Should -BeNullOrEmpty
-	}
+	}	
 }