diff --git a/src/MyWebLog.Domain/SupportTypes.fs b/src/MyWebLog.Domain/SupportTypes.fs
index 3d78e61..1266fd7 100644
--- a/src/MyWebLog.Domain/SupportTypes.fs
+++ b/src/MyWebLog.Domain/SupportTypes.fs
@@ -554,7 +554,27 @@ type PodcastOptions = {
     
     /// The medium (what the podcast IS, not what it is ABOUT)
     Medium: PodcastMedium option
-}
+} with
+    
+    /// A default set of podcast options
+    static member Empty = {
+        Title            = ""
+        Subtitle         = None
+        ItemsInFeed      = 0
+        Summary          = ""
+        DisplayedAuthor  = ""
+        Email            = ""
+        ImageUrl         = Permalink.Empty
+        AppleCategory    = ""
+        AppleSubcategory = None
+        Explicit         = No
+        DefaultMediaType = None
+        MediaBaseUrl     = None
+        PodcastGuid      = None
+        FundingUrl       = None
+        FundingText      = None
+        Medium           = None 
+    }
 
 
 /// A custom feed
diff --git a/src/MyWebLog.Domain/ViewModels.fs b/src/MyWebLog.Domain/ViewModels.fs
index 3b8a761..3bbdea0 100644
--- a/src/MyWebLog.Domain/ViewModels.fs
+++ b/src/MyWebLog.Domain/ViewModels.fs
@@ -89,7 +89,12 @@ type DisplayCustomFeed = {
     static member FromFeed (cats: DisplayCategory array) (feed: CustomFeed) =
         let source =
             match feed.Source with
-            | Category (CategoryId catId) -> $"Category: {(cats |> Array.find (fun cat -> cat.Id = catId)).Name}"
+            | Category (CategoryId catId) ->
+                cats
+                |> Array.tryFind (fun cat -> cat.Id = catId)
+                |> Option.map _.Name
+                |> Option.defaultValue "--INVALID; DELETE THIS FEED--"
+                |> sprintf "Category: %s"
             | Tag tag -> $"Tag: {tag}"
         {   Id        = string feed.Id
             Source    = source
diff --git a/src/MyWebLog.Tests/Domain.fs b/src/MyWebLog.Tests/Domain.fs
index 09c6374..78ffeb2 100644
--- a/src/MyWebLog.Tests/Domain.fs
+++ b/src/MyWebLog.Tests/Domain.fs
@@ -501,6 +501,75 @@ let webLogUserTests =
         ]
     ]
 
+// --- VIEW MODELS ---
+
+open MyWebLog.ViewModels
+
+/// Unit tests for the addBaseToRelativeUrls helper function
+let addBaseToRelativeUrlsTests =
+    testList "PublicHelpers.addBaseToRelativeUrls" [
+        test "succeeds when there is no extra URL path" {
+            let testText = """<a href="/somewhere-else.html">Howdy></a>"""
+            let modified = addBaseToRelativeUrls "" testText
+            Expect.equal modified testText "The text should not have been modified"
+        }
+        test "succeeds with an extra URL path" {
+            let testText =
+                """<a href="/my-link.htm"><img src="/pretty-picture.jpg"></a><a href="https://example.com>link</a>"""
+            let expected =
+                """<a href="/a/b/my-link.htm"><img src="/a/b/pretty-picture.jpg"></a><a href="https://example.com>link</a>"""
+            Expect.equal (addBaseToRelativeUrls "/a/b" testText) expected "Relative URLs not modified correctly"
+        }
+    ]
+
+/// Unit tests for the DisplayCustomFeed type
+let displayCustomFeedTests =
+    testList "DisplayCustomFeed.FromFeed" [
+        test "succeeds for a feed for an existing category" {
+            let cats =
+                [| { DisplayCategory.Id = "abc"
+                     Slug        = "a-b-c"
+                     Name        = "My Lovely Category"
+                     Description = None
+                     ParentNames = [||]
+                     PostCount   = 3 } |]
+            let feed =
+                { CustomFeed.Empty with
+                    Id     = CustomFeedId "test-feed"
+                    Source = Category (CategoryId "abc")
+                    Path   = Permalink "test-feed.xml" }
+            let model = DisplayCustomFeed.FromFeed cats feed
+            Expect.equal model.Id "test-feed" "Id not filled properly"
+            Expect.equal model.Source "Category: My Lovely Category" "Source not filled properly"
+            Expect.equal model.Path "test-feed.xml" "Path not filled properly"
+            Expect.isFalse model.IsPodcast "IsPodcast not filled properly"
+        }
+        test "succeeds for a feed for a non-existing category" {
+            let feed =
+                { CustomFeed.Empty with
+                    Id     = CustomFeedId "bad-feed"
+                    Source = Category (CategoryId "xyz")
+                    Path   = Permalink "trouble.xml" }
+            let model = DisplayCustomFeed.FromFeed [||] feed
+            Expect.equal model.Id "bad-feed" "Id not filled properly"
+            Expect.equal model.Source "Category: --INVALID; DELETE THIS FEED--" "Source not filled properly"
+            Expect.equal model.Path "trouble.xml" "Path not filled properly"
+            Expect.isFalse model.IsPodcast "IsPodcast not filled properly"
+        }
+        test "succeeds for a feed for a tag" {
+            let feed =
+                { Id      = CustomFeedId "tag-feed"
+                  Source  = Tag "testing"
+                  Path    = Permalink "testing-posts.xml"
+                  Podcast = Some PodcastOptions.Empty }
+            let model = DisplayCustomFeed.FromFeed [||] feed
+            Expect.equal model.Id "tag-feed" "Id not filled properly"
+            Expect.equal model.Source "Tag: testing" "Source not filled properly"
+            Expect.equal model.Path "testing-posts.xml" "Path not filled properly"
+            Expect.isTrue model.IsPodcast "IsPodcast not filled properly"
+        }
+    ]
+
 /// All tests for the Domain namespace
 let all =
     testList
@@ -519,4 +588,7 @@ let all =
           uploadDestinationTests
           // data types
           webLogTests
-          webLogUserTests ]
+          webLogUserTests
+          // view models
+          addBaseToRelativeUrlsTests
+          displayCustomFeedTests ]