diff --git a/src/Item/Set-CredentialStoreItem.Tests.ps1 b/src/Item/Set-CredentialStoreItem.Tests.ps1
new file mode 100644
index 0000000..218b812
--- /dev/null
+++ b/src/Item/Set-CredentialStoreItem.Tests.ps1
@@ -0,0 +1,130 @@
+[Diagnostics.CodeAnalysis.SuppressMessageAttribute(
+    'PSAvoidUsingConvertToSecureStringWithPlainText',
+    '',
+    Justification = 'just used in pester tests.'
+)]
+[Diagnostics.CodeAnalysis.SuppressMessageAttribute(
+    'PSProvideCommentHelp',
+    '',
+    Justification = 'no need in internal pester helpers.'
+)]
+param ()
+
+BeforeAll {
+    $ManifestFile = (Get-Item -Path "./src/*.psd1").FullName
+    Import-Module $ManifestFile -Force
+
+    $PrivateFunctions = (Get-ChildItem -Path "./src/Private/*.ps1" | Where-Object {
+            $_.BaseName -notmatch '.Tests'
+        }
+    ).FullName
+    foreach ( $func in $PrivateFunctions) {
+        . $func
+    }
+
+    # Backup existing credential stores
+    $VerbosePreference = "Continue"
+    Write-Verbose "Backup private Credential Store..."
+    $CSPath = Get-DefaultCredentialStorePath
+    $BackupFile = "{0}.back" -f $CSPath
+    if (Test-Path -Path $CSPath) {
+        Move-Item -Path $CSPath -Destination $BackupFile
+    }
+    Write-Verbose "Backup shared CredentialStore..."
+    $CSShared = Get-DefaultCredentialStorePath -Shared
+    $BackupSharedFile = "{0}.back" -f $CSShared
+    if (Test-Path -Path $CSShared) {
+        Move-Item -Path $CSShared -Destination $BackupSharedFile
+    }
+    Write-Verbose "Remove old CredentialStore in Temp dir"
+    $CSTemp = Join-Path -Path (Get-TempDir) -ChildPath '/CredentialStore.json'
+    if (Test-Path -Path $CSTemp) {
+        Remove-Item -Path $CSTemp
+    }
+    $VerbosePreference = "SilentlyContinue"
+}
+
+Describe 'New-CredentialStoreItem' {
+    Context 'Private Credential Store tests' {
+        It 'Add entry to a private store.' {
+            # Create a fresh CredentialStore first
+            New-CredentialStore -Force
+
+            # Define the content of the CredentialStoreItem.
+            $RemoteHost = 'barfoo'
+            $UserName = 'MyUser'
+            $Password = 'fooobarysdfsfs' | ConvertTo-SecureString -AsPlainText -Force
+
+            # Form the CredentialObject.
+            $creds = [PSCredential]::new($UserName, $Password)
+
+            # Create the CredentialStoreItem.
+            New-CredentialStoreItem -RemoteHost $RemoteHost -Credential $creds
+
+            # Formulate an update to the CredentialStoreItem.
+            $ClearPassword = 'fooobaryadfafa'
+            $Password = $ClearPassword | ConvertTo-SecureString -AsPlainText -Force
+            $creds = [PSCredential]::new($UserName, $Password)
+            {
+                Set-CredentialStoreItem -RemoteHost $RemoteHost -Credential $creds
+            } | Should -Not -Throw
+
+            # Control the content of the CredentialStore.
+            $content = Get-CredentialStoreItem -RemoteHost $RemoteHost
+            $content.GetNetworkCredential().Password | Should -Be $ClearPassword
+        }
+    }
+    Context 'Shared Credential Store tests' {
+        It 'Add entry to a shared store.' {
+            # Create a fresh CredentialStore first
+            $tmpCS = Join-Path -Path (Get-TempDir) -ChildPath '/CredentialStore.json'
+            New-CredentialStore -Path $tmpCS -Force -Shared
+
+            # Define the content of the CredentialStoreItem.
+            $RemoteHost = 'barfoo'
+            $UserName = 'MyUser'
+            $Password = 'fooobarysdfsfs' | ConvertTo-SecureString -AsPlainText -Force
+
+            # Form the CredentialObject.
+            $creds = [PSCredential]::new($UserName, $Password)
+
+            # Create the CredentialStoreItem.
+            New-CredentialStoreItem -RemoteHost $RemoteHost -Credential $creds -Path $tmpCS -Shared
+
+            # Formulate an update to the CredentialStoreItem.
+            $ClearPassword = 'fooobaryadfafa'
+            $Password = $ClearPassword | ConvertTo-SecureString -AsPlainText -Force
+            $creds = [PSCredential]::new($UserName, $Password)
+
+            {
+                Set-CredentialStoreItem -RemoteHost $RemoteHost -Credential $creds -Path $tmpCS -Shared
+            } | Should -Not -Throw
+
+            # Control the content of the CredentialStore.
+            $content = Get-CredentialStoreItem -RemoteHost $RemoteHost -Path $tmpCS -Shared
+            $content.GetNetworkCredential().Password | Should -Be $ClearPassword
+        }
+    }
+}
+
+AfterAll {
+    # Cleanup test stores and restore existing ones.
+    $VerbosePreference = "Continue"
+    Write-Verbose "Restoring private CredentialStore"
+    If (Test-Path -Path $BackupFile) {
+        If (Test-Path -Path $CSPath) {
+            Remove-Item -Path $CSPath
+            Move-Item -Path $BackupFile -Destination $CSPath
+        }
+    }
+
+    Write-Verbose "Restoring shared CredentialStore"
+    If (Test-Path -Path $BackupSharedFile) {
+        If (Test-Path -Path $CSShared) {
+            Remove-Item -Path $CSShared
+            Move-Item -Path $BackupSharedFile -Destination $CSShared
+        }
+    }
+    $VerbosePreference = "SilentlyContinue"
+
+}