Fixed unit tests

src/types.zig

@@ -134,7 +134,7 @@ pub const TextDocument = struct {
     };
 
     pub fn borrowNullTerminatedSlice(self: *const @This(), start_idx: usize, end_idx: usize) Held {
-        std.debug.assert(end_idx >= start_idx and end_idx < self.text.len);
+        std.debug.assert(end_idx >= start_idx);
         const popped_char = self.mem[end_idx];
         self.mem[end_idx] = 0;
         return .{

src/unit_tests.zig

@@ -8,13 +8,14 @@ const std = @import("std");
 const allocator = std.testing.allocator;
 
 fn makeDocument(uri: []const u8, text: []const u8) !types.TextDocument {
-    const mem = try allocator.alloc(u8, text.len);
+    const mem = try allocator.alloc(u8, text.len + 1);
     std.mem.copy(u8, mem, text);
+    mem[text.len] = 0;
 
     return types.TextDocument{
         .uri = uri,
         .mem = mem,
-        .text = mem[0..],
+        .text = mem[0..text.len :0],
     };
 }