1 files changed, 42 insertions, 0 deletions
diff --git a/Tests/NorgKitTests/Helpers/ASCIIByteSetTests.swift b/Tests/NorgKitTests/Helpers/ASCIIByteSetTests.swift
new file mode 100644
index 0000000..eb29ecb
--- /dev/null
+++ b/Tests/NorgKitTests/Helpers/ASCIIByteSetTests.swift
@@ -0,0 +1,42 @@
+import Testing
+
+@testable import NorgKit
+
+struct ASCIIByteSetTests {
+
+  @Test func containsLowBytes() {
+    // `*` (0x2A) and `-` (0x2D) live in the low 64-bit word.
+    let set = ASCIIByteSet("*-")
+    #expect(set.contains(UInt8(ascii: "*")))
+    #expect(set.contains(UInt8(ascii: "-")))
+    #expect(!set.contains(UInt8(ascii: "/")))
+  }
+
+  @Test func containsHighBytes() {
+    // `~` (0x7E) and `_` (0x5F) live in the high 64-bit word.
+    let set = ASCIIByteSet("~_")
+    #expect(set.contains(UInt8(ascii: "~")))
+    #expect(set.contains(UInt8(ascii: "_")))
+    #expect(!set.contains(UInt8(ascii: "x")))
+  }
+
+  @Test func spansBothWords() {
+    let set = ASCIIByteSet("*~")
+    #expect(set.contains(UInt8(ascii: "*")))
+    #expect(set.contains(UInt8(ascii: "~")))
+  }
+
+  @Test func rejectsNonAsciiAndOutOfSetBytes() {
+    let set = ASCIIByteSet("*")
+    #expect(!set.contains(0))  // NUL, low word, unset
+    #expect(!set.contains(200))  // beyond ASCII, never stored
+    #expect(!set.contains(127))  // high word, unset
+  }
+
+  @Test func emptySetContainsNothing() {
+    let set = ASCIIByteSet("")
+    #expect(!set.contains(UInt8(ascii: "*")))
+    #expect(!set.contains(0))
+    #expect(!set.contains(127))
+  }
+}