diff --git a/src/MyWebLog.Domain/SupportTypes.fs b/src/MyWebLog.Domain/SupportTypes.fs
index c424dad..3d78e61 100644
--- a/src/MyWebLog.Domain/SupportTypes.fs
+++ b/src/MyWebLog.Domain/SupportTypes.fs
@@ -660,7 +660,10 @@ type ThemeAssetId =
     /// Convert a string into a theme asset ID
     static member Parse(it : string) =
         let themeIdx = it.IndexOf "/"
-        ThemeAssetId(ThemeId it[..(themeIdx - 1)], it[(themeIdx + 1)..])
+        if themeIdx < 0 then
+            invalidArg "id" $"Invalid format; expected [theme_id]/[asset_id] (received {it})"
+        else
+            ThemeAssetId(ThemeId it[..(themeIdx - 1)], it[(themeIdx + 1)..])
     
     /// Convert a theme asset ID into a path string
     override this.ToString() =
diff --git a/src/MyWebLog.Tests/Domain.fs b/src/MyWebLog.Tests/Domain.fs
index b97a0e4..afdef76 100644
--- a/src/MyWebLog.Tests/Domain.fs
+++ b/src/MyWebLog.Tests/Domain.fs
@@ -176,6 +176,245 @@ let explicitRatingTests =
         ]
     ]
 
+/// Tests for the Episode type
+let episodeTests =
+    testList "Episode" [
+        testList "FormatDuration" [
+            test "succeeds when no duration is specified" {
+                Expect.isNone (Episode.Empty.FormatDuration()) "A missing duration should have returned None"
+            }
+            test "succeeds when duration is specified" {
+                Expect.equal
+                    ({ Episode.Empty with
+                        Duration = Some (Duration.FromMinutes 3L + Duration.FromSeconds 13L) }.FormatDuration())
+                    (Some "0:03:13")
+                    "Duration not formatted correctly"
+            }
+            test "succeeds when duration is > 10 hours" {
+                Expect.equal
+                    ({ Episode.Empty with Duration = Some (Duration.FromHours 11) }.FormatDuration())
+                    (Some "11:00:00")
+                    "Duration not formatted correctly"
+            }
+        ]
+    ]
+
+/// Unit tests for the MarkupText type
+let markupTextTests =
+    testList "MarkupText" [
+        testList "Parse" [
+            test "succeeds with HTML content" {
+                let txt = MarkupText.Parse "HTML: <p>howdy</p>"
+                match txt with
+                | Html it when it = "<p>howdy</p>" -> ()
+                | _ -> Expect.isTrue false $"Unexpected parse result for HTML: %A{txt}"
+            }
+            test "succeeds with Markdown content" {
+                let txt = MarkupText.Parse "Markdown: # A Title"
+                match txt with
+                | Markdown it when it = "# A Title" -> ()
+                | _ -> Expect.isTrue false $"Unexpected parse result for Markdown: %A{txt}"
+            }
+            test "fails with unexpected content" {
+                Expect.throwsT<ArgumentException>
+                    (fun () -> ignore (MarkupText.Parse "LaTEX: nope")) "Invalid value should have raised an exception"
+            }
+        ]
+        testList "SourceType" [
+            test "succeeds for HTML" {
+                Expect.equal (MarkupText.Parse "HTML: something").SourceType "HTML" "HTML source type incorrect"
+            }
+            test "succeeds for Markdown" {
+                Expect.equal (MarkupText.Parse "Markdown: blah").SourceType "Markdown" "Markdown source type incorrect"
+            }
+        ]
+        testList "Text" [
+            test "succeeds for HTML" {
+                Expect.equal (MarkupText.Parse "HTML: test").Text "test" "HTML text incorrect"
+            }
+            test "succeeds for Markdown" {
+                Expect.equal (MarkupText.Parse "Markdown: test!").Text "test!" "Markdown text incorrect"
+            }
+        ]
+        testList "ToString" [
+            test "succeeds for HTML" {
+                Expect.equal
+                    (string (MarkupText.Parse "HTML: <h1>HTML</h1>"))
+                    "HTML: <h1>HTML</h1>"
+                    "HTML string value incorrect"
+            }
+            test "succeeds for Markdown" {
+                Expect.equal
+                    (string (MarkupText.Parse "Markdown: # Some Content"))
+                    "Markdown: # Some Content"
+                    "Markdown string value incorrect"
+            }
+        ]
+        testList "AsHtml" [
+            test "succeeds for HTML" {
+                Expect.equal
+                    ((MarkupText.Parse "HTML: <h1>The Heading</h1>").AsHtml())
+                    "<h1>The Heading</h1>"
+                    "HTML value incorrect"
+            }
+            test "succeeds for Markdown" {
+                Expect.equal
+                    ((MarkupText.Parse "Markdown: *emphasis*").AsHtml())
+                    "<p><em>emphasis</em></p>\n"
+                    "Markdown HTML value incorrect"
+            }
+        ]
+    ]
+
+/// Unit tests for the PodcastMedium type
+let podcastMediumTests =
+    testList "PodcastMedium" [
+        testList "Parse" [
+            test "succeeds for \"podcast\"" {
+                Expect.equal (PodcastMedium.Parse "podcast") Podcast "\"podcast\" not parsed correctly"
+            }
+            test "succeeds for \"music\"" {
+                Expect.equal (PodcastMedium.Parse "music") Music "\"music\" not parsed correctly"
+            }
+            test "succeeds for \"video\"" {
+                Expect.equal (PodcastMedium.Parse "video") Video "\"video\" not parsed correctly"
+            }
+            test "succeeds for \"film\"" {
+                Expect.equal (PodcastMedium.Parse "film") Film "\"film\" not parsed correctly"
+            }
+            test "succeeds for \"audiobook\"" {
+                Expect.equal (PodcastMedium.Parse "audiobook") Audiobook "\"audiobook\" not parsed correctly"
+            }
+            test "succeeds for \"newsletter\"" {
+                Expect.equal (PodcastMedium.Parse "newsletter") Newsletter "\"newsletter\" not parsed correctly"
+            }
+            test "succeeds for \"blog\"" {
+                Expect.equal (PodcastMedium.Parse "blog") Blog "\"blog\" not parsed correctly"
+            }
+            test "fails for invalid type" {
+                Expect.throwsT<ArgumentException>
+                    (fun () -> ignore (PodcastMedium.Parse "laser")) "Invalid value should have raised an exception"
+            }
+        ]
+        testList "ToString" [
+            test "succeeds for Podcast" {
+                Expect.equal (string Podcast) "podcast" "Podcast string incorrect"
+            }
+            test "succeeds for Music" {
+                Expect.equal (string Music) "music" "Music string incorrect"
+            }
+            test "succeeds for Video" {
+                Expect.equal (string Video) "video" "Video string incorrect"
+            }
+            test "succeeds for Film" {
+                Expect.equal (string Film) "film" "Film string incorrect"
+            }
+            test "succeeds for Audiobook" {
+                Expect.equal (string Audiobook) "audiobook" "Audiobook string incorrect"
+            }
+            test "succeeds for Newsletter" {
+                Expect.equal (string Newsletter) "newsletter" "Newsletter string incorrect"
+            }
+            test "succeeds for Blog" {
+                Expect.equal (string Blog) "blog" "Blog string incorrect"
+            }
+        ]
+    ]
+
+/// Unit tests for the PostStatus type
+let postStatusTests =
+    testList "PostStatus" [
+        testList "Parse" [
+            test "succeeds for \"Draft\"" {
+                Expect.equal (PostStatus.Parse "Draft") Draft "\"Draft\" not parsed correctly"
+            }
+            test "succeeds for \"Published\"" {
+                Expect.equal (PostStatus.Parse "Published") Published "\"Published\" not parsed correctly"
+            }
+            test "fails for unrecognized value" {
+                Expect.throwsT<ArgumentException>
+                    (fun () -> ignore (PostStatus.Parse "Rescinded")) "Invalid value should have raised an exception"
+            }
+        ]
+    ]
+
+/// Unit tests for the CustomFeedSource type
+let customFeedSourceTests =
+    testList "CustomFeedSource" [
+        testList "Parse" [
+            test "succeeds for category feeds" {
+                Expect.equal
+                    (CustomFeedSource.Parse "category:abc123")
+                    (Category (CategoryId "abc123"))
+                    "Category feed not parsed correctly"
+            }
+            test "succeeds for tag feeds" {
+                Expect.equal (CustomFeedSource.Parse "tag:turtles") (Tag "turtles") "Tag feed not parsed correctly"
+            }
+            test "fails for unknown type" {
+                Expect.throwsT<ArgumentException>
+                    (fun () -> ignore (CustomFeedSource.Parse "nasa:sat1"))
+                    "Invalid value should have raised an exception"
+            }
+        ]
+        testList "ToString" [
+            test "succeeds for category feed" {
+                Expect.equal
+                    (string (CustomFeedSource.Parse "category:fish")) "category:fish" "Category feed string incorrect"
+            }
+            test "succeeds for tag feed" {
+                Expect.equal (string (CustomFeedSource.Parse "tag:rocks")) "tag:rocks" "Tag feed string incorrect"
+            }
+        ]
+    ]
+
+/// Unit tests for the ThemeAssetId type
+let themeAssetIdTests =
+    testList "ThemeAssetId" [
+        testList "Parse" [
+            test "succeeds with expected values" {
+                Expect.equal
+                    (ThemeAssetId.Parse "test-theme/the-asset")
+                    (ThemeAssetId ((ThemeId "test-theme"), "the-asset"))
+                    "Theme asset ID not parsed correctly"
+            }
+            test "fails if no slash is present" {
+                Expect.throwsT<ArgumentException>
+                    (fun () -> ignore (ThemeAssetId.Parse "my-theme-asset"))
+                    "Invalid value should have raised an exception"
+            }
+        ]
+        test "ToString succeeds" {
+            Expect.equal
+                (string (ThemeAssetId ((ThemeId "howdy"), "pardner"))) "howdy/pardner" "Theme asset ID string incorrect"
+        }
+    ]
+
+/// Unit tests for the UploadDestination type
+let uploadDestinationTests =
+    testList "UploadDestination" [
+        testList "Parse" [
+            test "succeeds for \"Database\"" {
+                Expect.equal (UploadDestination.Parse "Database") Database "\"Database\" not parsed correctly"
+            }
+            test "succeeds for \"Disk\"" {
+                Expect.equal (UploadDestination.Parse "Disk") Database "\"Disk\" not parsed correctly"
+            }
+            test "fails for unrecognized value" {
+                Expect.throwsT<ArgumentException>
+                    (fun () -> ignore (UploadDestination.Parse "Azure")) "Invalid value should have raised an exception"
+            }
+        ]
+        testList "ToString" [
+            test "succeeds for Database" {
+                Expect.equal (string Database) "Database" "Database string incorrect"
+            }
+            test "succeeds for Disk" {
+                Expect.equal (string Disk) "Disk" "Disk string incorrect"
+            }
+        ]
+    ]
+
 /// All tests for the Domain namespace
 let all =
     testList
@@ -183,4 +422,11 @@ let all =
         [ nodaTests
           accessLevelTests
           commentStatusTests
-          explicitRatingTests ]
+          explicitRatingTests
+          episodeTests
+          markupTextTests
+          podcastMediumTests
+          postStatusTests
+          customFeedSourceTests
+          themeAssetIdTests
+          uploadDestinationTests ]