diff --git a/test/compile_errors.zig b/test/compile_errors.zig
index 8472cfbf7e..669970aee7 100644
--- a/test/compile_errors.zig
+++ b/test/compile_errors.zig
@@ -4,8 +4,7 @@ const Cases = @import("src/Cases.zig");
 
 pub fn addCases(ctx: *Cases, b: *std.Build) !void {
     {
-        const case = ctx.obj("multiline error messages", b.graph.host);
-
+        const case = ctx.obj("multiline error message", b.graph.host);
         case.addError(
             \\comptime {
             \\    @compileError("hello\nworld");
@@ -14,7 +13,10 @@ pub fn addCases(ctx: *Cases, b: *std.Build) !void {
             \\:2:5: error: hello
             \\             world
         });
+    }
 
+    {
+        const case = ctx.obj("multiline error message with trailing newline", b.graph.host);
         case.addError(
             \\comptime {
             \\    @compileError(
diff --git a/test/nvptx.zig b/test/nvptx.zig
index dd68e8a7de..dce924115a 100644
--- a/test/nvptx.zig
+++ b/test/nvptx.zig
@@ -91,9 +91,10 @@ fn addPtx(ctx: *Cases, target: std.Build.ResolvedTarget, name: []const u8) *Case
     ctx.cases.append(.{
         .name = name,
         .target = target,
-        .updates = std.ArrayList(Cases.Update).init(ctx.cases.allocator),
+        .files = .init(ctx.arena),
+        .case = null,
         .output_mode = .Obj,
-        .deps = std.ArrayList(Cases.DepModule).init(ctx.cases.allocator),
+        .deps = .init(ctx.arena),
         .link_libc = false,
         .emit_bin = false,
         .backend = .llvm,
diff --git a/test/src/Cases.zig b/test/src/Cases.zig
index f386bc3d63..e69bde0904 100644
--- a/test/src/Cases.zig
+++ b/test/src/Cases.zig
@@ -2,50 +2,11 @@ gpa: Allocator,
 arena: Allocator,
 cases: std.ArrayList(Case),
 translate: std.ArrayList(Translate),
-incremental_cases: std.ArrayList(IncrementalCase),
 
 pub const IncrementalCase = struct {
     base_path: []const u8,
 };
 
-pub const Update = struct {
-    /// The input to the current update. We simulate an incremental update
-    /// with the file's contents changed to this value each update.
-    ///
-    /// This value can change entirely between updates, which would be akin
-    /// to deleting the source file and creating a new one from scratch; or
-    /// you can keep it mostly consistent, with small changes, testing the
-    /// effects of the incremental compilation.
-    files: std.ArrayList(File),
-    /// This is a description of what happens with the update, for debugging
-    /// purposes.
-    name: []const u8,
-    case: union(enum) {
-        /// Check that it compiles with no errors.
-        Compile: void,
-        /// Check the main binary output file against an expected set of bytes.
-        /// This is most useful with, for example, `-ofmt=c`.
-        CompareObjectFile: []const u8,
-        /// An error update attempts to compile bad code, and ensures that it
-        /// fails to compile, and for the expected reasons.
-        /// A slice containing the expected stderr template, which
-        /// gets some values substituted.
-        Error: []const []const u8,
-        /// An execution update compiles and runs the input, testing the
-        /// stdout against the expected results
-        /// This is a slice containing the expected message.
-        Execution: []const u8,
-        /// A header update compiles the input with the equivalent of
-        /// `-femit-h` and tests the produced header against the
-        /// expected result.
-        Header: []const u8,
-    },
-
-    pub fn addSourceFile(update: *Update, name: []const u8, src: [:0]const u8) void {
-        update.files.append(.{ .path = name, .src = src }) catch @panic("out of memory");
-    }
-};
-
 pub const File = struct {
     src: [:0]const u8,
     path: []const u8,
@@ -67,9 +28,6 @@ pub const CFrontend = enum {
     aro,
 };
 
-/// A `Case` consists of a list of `Update`. The same `Compilation` is used for each
-/// update, so each update's source is treated as a single file being
-/// updated by the test harness and incrementally compiled.
 pub const Case = struct {
     /// The name of the test case. This is shown if a test fails, and
     /// otherwise ignored.
@@ -81,7 +39,29 @@ pub const Case = struct {
     /// to Executable.
     output_mode: std.builtin.OutputMode,
     optimize_mode: std.builtin.OptimizeMode = .Debug,
-    updates: std.ArrayList(Update),
+
+    files: std.ArrayList(File),
+    case: ?union(enum) {
+        /// Check that it compiles with no errors.
+        Compile: void,
+        /// Check the main binary output file against an expected set of bytes.
+        /// This is most useful with, for example, `-ofmt=c`.
+        CompareObjectFile: []const u8,
+        /// An error update attempts to compile bad code, and ensures that it
+        /// fails to compile, and for the expected reasons.
+        /// A slice containing the expected stderr template, which
+        /// gets some values substituted.
+        Error: []const []const u8,
+        /// An execution update compiles and runs the input, testing the
+        /// stdout against the expected results
+        /// This is a slice containing the expected message.
+        Execution: []const u8,
+        /// A header update compiles the input with the equivalent of
+        /// `-femit-h` and tests the produced header against the
+        /// expected result.
+        Header: []const u8,
+    },
+
     emit_bin: bool = true,
     emit_h: bool = false,
     is_test: bool = false,
@@ -99,8 +79,7 @@ pub const Case = struct {
     deps: std.ArrayList(DepModule),
 
     pub fn addSourceFile(case: *Case, name: []const u8, src: [:0]const u8) void {
-        const update = &case.updates.items[case.updates.items.len - 1];
-        update.files.append(.{ .path = name, .src = src }) catch @panic("OOM");
+        case.files.append(.{ .path = name, .src = src }) catch @panic("OOM");
     }
 
     pub fn addDepModule(case: *Case, name: []const u8, path: []const u8) void {
@@ -113,46 +92,28 @@ pub const Case = struct {
     /// Adds a subcase in which the module is updated with `src`, compiled,
     /// run, and the output is tested against `result`.
     pub fn addCompareOutput(self: *Case, src: [:0]const u8, result: []const u8) void {
-        self.updates.append(.{
-            .files = std.ArrayList(File).init(self.updates.allocator),
-            .name = "update",
-            .case = .{ .Execution = result },
-        }) catch @panic("out of memory");
-        addSourceFile(self, "tmp.zig", src);
-    }
-
-    pub fn addError(self: *Case, src: [:0]const u8, errors: []const []const u8) void {
-        return self.addErrorNamed("update", src, errors);
+        assert(self.case == null);
+        self.case = .{ .Execution = result };
+        self.addSourceFile("tmp.zig", src);
     }
 
     /// Adds a subcase in which the module is updated with `src`, which
     /// should contain invalid input, and ensures that compilation fails
     /// for the expected reasons, given in sequential order in `errors` in
     /// the form `:line:column: error: message`.
-    pub fn addErrorNamed(
-        self: *Case,
-        name: []const u8,
-        src: [:0]const u8,
-        errors: []const []const u8,
-    ) void {
+    pub fn addError(self: *Case, src: [:0]const u8, errors: []const []const u8) void {
         assert(errors.len != 0);
-        self.updates.append(.{
-            .files = std.ArrayList(File).init(self.updates.allocator),
-            .name = name,
-            .case = .{ .Error = errors },
-        }) catch @panic("out of memory");
-        addSourceFile(self, "tmp.zig", src);
+        assert(self.case == null);
+        self.case = .{ .Error = errors };
+        self.addSourceFile("tmp.zig", src);
     }
 
     /// Adds a subcase in which the module is updated with `src`, and
     /// asserts that it compiles without issue
     pub fn addCompile(self: *Case, src: [:0]const u8) void {
-        self.updates.append(.{
-            .files = std.ArrayList(File).init(self.updates.allocator),
-            .name = "compile",
-            .case = .{ .Compile = {} },
-        }) catch @panic("out of memory");
-        addSourceFile(self, "tmp.zig", src);
+        assert(self.case == null);
+        self.case = .Compile;
+        self.addSourceFile("tmp.zig", src);
     }
 };
 
@@ -180,10 +141,11 @@ pub fn addExe(
     name: []const u8,
     target: std.Build.ResolvedTarget,
 ) *Case {
-    ctx.cases.append(Case{
+    ctx.cases.append(.{
         .name = name,
         .target = target,
-        .updates = std.ArrayList(Update).init(ctx.cases.allocator),
+        .files = .init(ctx.arena),
+        .case = null,
         .output_mode = .Exe,
         .deps = std.ArrayList(DepModule).init(ctx.arena),
     }) catch @panic("out of memory");
@@ -198,10 +160,11 @@ pub fn exe(ctx: *Cases, name: []const u8, target: std.Build.ResolvedTarget) *Cas
 pub fn exeFromCompiledC(ctx: *Cases, name: []const u8, target_query: std.Target.Query, b: *std.Build) *Case {
     var adjusted_query = target_query;
     adjusted_query.ofmt = .c;
-    ctx.cases.append(Case{
+    ctx.cases.append(.{
         .name = name,
         .target = b.resolveTargetQuery(adjusted_query),
-        .updates = std.ArrayList(Update).init(ctx.cases.allocator),
+        .files = .init(ctx.arena),
+        .case = null,
         .output_mode = .Exe,
         .deps = std.ArrayList(DepModule).init(ctx.arena),
         .link_libc = true,
@@ -210,10 +173,11 @@ pub fn exeFromCompiledC(ctx: *Cases, name: []const u8, target_query: std.Target.
 }
 
 pub fn addObjLlvm(ctx: *Cases, name: []const u8, target: std.Build.ResolvedTarget) *Case {
-    ctx.cases.append(Case{
+    ctx.cases.append(.{
         .name = name,
         .target = target,
-        .updates = std.ArrayList(Update).init(ctx.cases.allocator),
+        .files = .init(ctx.arena),
+        .case = null,
         .output_mode = .Obj,
         .deps = std.ArrayList(DepModule).init(ctx.arena),
         .backend = .llvm,
@@ -226,10 +190,11 @@ pub fn addObj(
     name: []const u8,
     target: std.Build.ResolvedTarget,
 ) *Case {
-    ctx.cases.append(Case{
+    ctx.cases.append(.{
         .name = name,
         .target = target,
-        .updates = std.ArrayList(Update).init(ctx.cases.allocator),
+        .files = .init(ctx.arena),
+        .case = null,
         .output_mode = .Obj,
         .deps = std.ArrayList(DepModule).init(ctx.arena),
     }) catch @panic("out of memory");
@@ -241,10 +206,11 @@ pub fn addTest(
     name: []const u8,
     target: std.Build.ResolvedTarget,
 ) *Case {
-    ctx.cases.append(Case{
+    ctx.cases.append(.{
         .name = name,
         .target = target,
-        .updates = std.ArrayList(Update).init(ctx.cases.allocator),
+        .files = .init(ctx.arena),
+        .case = null,
         .output_mode = .Exe,
         .is_test = true,
         .deps = std.ArrayList(DepModule).init(ctx.arena),
@@ -266,10 +232,11 @@ pub fn objZIR(ctx: *Cases, name: []const u8, target: std.Build.ResolvedTarget) *
 pub fn addC(ctx: *Cases, name: []const u8, target: std.Build.ResolvedTarget) *Case {
     var target_adjusted = target;
     target_adjusted.ofmt = std.Target.ObjectFormat.c;
-    ctx.cases.append(Case{
+    ctx.cases.append(.{
         .name = name,
         .target = target_adjusted,
-        .updates = std.ArrayList(Update).init(ctx.cases.allocator),
+        .files = .init(ctx.arena),
+        .case = null,
         .output_mode = .Obj,
         .deps = std.ArrayList(DepModule).init(ctx.arena),
     }) catch @panic("out of memory");
@@ -352,9 +319,7 @@ pub fn addCompile(
     ctx.addObj(name, target).addCompile(src);
 }
 
-/// Adds a test for each file in the provided directory.
-/// Testing strategy (TestStrategy) is inferred automatically from filenames.
-/// Recurses nested directories.
+/// Adds a test for each file in the provided directory. Recurses nested directories.
 ///
 /// Each file should include a test manifest as a contiguous block of comments at
 /// the end of the file. The first line should be the test type, followed by a set of
@@ -379,29 +344,18 @@ fn addFromDirInner(
     b: *std.Build,
 ) !void {
     var it = try iterable_dir.walk(ctx.arena);
-    var filenames = std.ArrayList([]const u8).init(ctx.arena);
+    var filenames: std.ArrayListUnmanaged([]const u8) = .empty;
 
     while (try it.next()) |entry| {
         if (entry.kind != .file) continue;
 
         // Ignore stuff such as .swp files
         if (!knownFileExtension(entry.basename)) continue;
-        try filenames.append(try ctx.arena.dupe(u8, entry.path));
+        try filenames.append(ctx.arena, try ctx.arena.dupe(u8, entry.path));
     }
 
-    // Sort filenames, so that incremental tests are contiguous and in-order
-    sortTestFilenames(filenames.items);
-
-    var test_it = TestIterator{ .filenames = filenames.items };
-    while (test_it.next()) |maybe_batch| {
-        const batch = maybe_batch orelse break;
-        const strategy: TestStrategy = if (batch.len > 1) .incremental else .independent;
-        const filename = batch[0];
+    for (filenames.items) |filename| {
         current_file.* = filename;
-        if (strategy == .incremental) {
-            try ctx.incremental_cases.append(.{ .base_path = filename });
-            continue;
-        }
 
         const max_file_size = 10 * 1024 * 1024;
         const src = try iterable_dir.readFileAllocOptions(ctx.arena, filename, max_file_size, null, 1, 0);
@@ -482,7 +436,8 @@ fn addFromDirInner(
                     .name = std.fs.path.stem(filename),
                     .import_path = std.fs.path.dirname(filename),
                     .backend = backend,
-                    .updates = std.ArrayList(Cases.Update).init(ctx.cases.allocator),
+                    .files = .init(ctx.arena),
+                    .case = null,
                     .emit_bin = emit_bin,
                     .is_test = is_test,
                     .output_mode = output_mode,
@@ -516,10 +471,6 @@ fn addFromDirInner(
                 .cli => @panic("TODO cli tests"),
             }
         }
-    } else |err| {
-        // make sure the current file is set to the file that produced an error
-        current_file.* = test_it.currentFilename();
-        return err;
     }
 }
 
@@ -528,7 +479,6 @@ pub fn init(gpa: Allocator, arena: Allocator) Cases {
         .gpa = gpa,
         .cases = std.ArrayList(Case).init(gpa),
         .translate = std.ArrayList(Translate).init(gpa),
-        .incremental_cases = std.ArrayList(IncrementalCase).init(gpa),
         .arena = arena,
     };
 }
@@ -633,26 +583,7 @@ pub fn lowerToBuildSteps(
         std.debug.panic("unable to detect native host: {s}\n", .{@errorName(err)});
     const cases_dir_path = b.build_root.join(b.allocator, &.{ "test", "cases" }) catch @panic("OOM");
 
-    for (self.incremental_cases.items) |incr_case| {
-        if (true) {
-            // TODO: incremental tests are disabled for now, as incremental compilation bugs were
-            // getting in the way of practical improvements to the compiler, and incremental
-            // compilation is not currently used. They should be re-enabled once incremental
-            // compilation is in a happier state.
-            continue;
-        }
-        // TODO: the logic for running these was bad, so I've ripped it out. Rewrite this
-        // in a way that actually spawns the compiler, communicating with it over the
-        // compiler server protocol.
-        _ = incr_case;
-        @panic("TODO implement incremental test case executor");
-    }
-
     for (self.cases.items) |case| {
-        if (case.updates.items.len != 1) continue; // handled with incremental_cases above
-        assert(case.updates.items.len == 1);
-        const update = case.updates.items[0];
-
         for (test_filters) |test_filter| {
             if (std.mem.indexOf(u8, case.name, test_filter)) |_| break;
         } else if (test_filters.len > 0) continue;
@@ -668,10 +599,10 @@ pub fn lowerToBuildSteps(
         const writefiles = b.addWriteFiles();
         var file_sources = std.StringHashMap(std.Build.LazyPath).init(b.allocator);
         defer file_sources.deinit();
-        const first_file = update.files.items[0];
+        const first_file = case.files.items[0];
         const root_source_file = writefiles.add(first_file.path, first_file.src);
         file_sources.put(first_file.path, root_source_file) catch @panic("OOM");
-        for (update.files.items[1..]) |file| {
+        for (case.files.items[1..]) |file| {
             file_sources.put(file.path, writefiles.add(file.path, file.src)) catch @panic("OOM");
         }
 
@@ -730,7 +661,7 @@ pub fn lowerToBuildSteps(
             },
         }
 
-        switch (update.case) {
+        switch (case.case.?) {
             .Compile => {
                 // Force the binary to be emitted if requested.
                 if (case.emit_bin) {
@@ -787,149 +718,6 @@ pub fn lowerToBuildSteps(
     }
 }
 
-/// Sort test filenames in-place, so that incremental test cases ("foo.0.zig",
-/// "foo.1.zig", etc.) are contiguous and appear in numerical order.
-fn sortTestFilenames(filenames: [][]const u8) void {
-    const Context = struct {
-        pub fn lessThan(_: @This(), a: []const u8, b: []const u8) bool {
-            const a_parts = getTestFileNameParts(a);
-            const b_parts = getTestFileNameParts(b);
-
-            // Sort "<base_name>.X.<file_ext>" based on "<base_name>" and "<file_ext>" first
-            return switch (std.mem.order(u8, a_parts.base_name, b_parts.base_name)) {
-                .lt => true,
-                .gt => false,
-                .eq => switch (std.mem.order(u8, a_parts.file_ext, b_parts.file_ext)) {
-                    .lt => true,
-                    .gt => false,
-                    .eq => {
-                        // a and b differ only in their ".X" part
-
-                        // Sort "<base_name>.<file_ext>" before any "<base_name>.X.<file_ext>"
-                        if (a_parts.test_index) |a_index| {
-                            if (b_parts.test_index) |b_index| {
-                                // Make sure that incremental tests appear in linear order
-                                return a_index < b_index;
-                            } else {
-                                return false;
-                            }
-                        } else {
-                            return b_parts.test_index != null;
-                        }
-                    },
-                },
-            };
-        }
-    };
-    std.mem.sort([]const u8, filenames, Context{}, Context.lessThan);
-}
-
-/// Iterates a set of filenames extracting batches that are either incremental
-/// ("foo.0.zig", "foo.1.zig", etc.) or independent ("foo.zig", "bar.zig", etc.).
-/// Assumes filenames are sorted.
-const TestIterator = struct {
-    start: usize = 0,
-    end: usize = 0,
-    filenames: []const []const u8,
-    /// reset on each call to `next`
-    index: usize = 0,
-
-    const Error = error{InvalidIncrementalTestIndex};
-
-    fn next(it: *TestIterator) Error!?[]const []const u8 {
-        try it.nextInner();
-        if (it.start == it.end) return null;
-        return it.filenames[it.start..it.end];
-    }
-
-    fn nextInner(it: *TestIterator) Error!void {
-        it.start = it.end;
-        if (it.end == it.filenames.len) return;
-        if (it.end + 1 == it.filenames.len) {
-            it.end += 1;
-            return;
-        }
-
-        const remaining = it.filenames[it.end..];
-        it.index = 0;
-        while (it.index < remaining.len - 1) : (it.index += 1) {
-            // First, check if this file is part of an incremental update sequence
-            // Split filename into "<base_name>.<index>.<file_ext>"
-            const prev_parts = getTestFileNameParts(remaining[it.index]);
-            const new_parts = getTestFileNameParts(remaining[it.index + 1]);
-
-            // If base_name and file_ext match, these files are in the same test sequence
-            // and the new one should be the incremented version of the previous test
-            if (std.mem.eql(u8, prev_parts.base_name, new_parts.base_name) and
-                std.mem.eql(u8, prev_parts.file_ext, new_parts.file_ext))
-            {
-                // This is "foo.X.zig" followed by "foo.Y.zig". Make sure that X = Y + 1
-                if (prev_parts.test_index == null)
-                    return error.InvalidIncrementalTestIndex;
-                if (new_parts.test_index == null)
-                    return error.InvalidIncrementalTestIndex;
-                if (new_parts.test_index.? != prev_parts.test_index.? + 1)
-                    return error.InvalidIncrementalTestIndex;
-            } else {
-                // This is not the same test sequence, so the new file must be the first file
-                // in a new sequence ("*.0.zig") or an independent test file ("*.zig")
-                if (new_parts.test_index != null and new_parts.test_index.? != 0)
-                    return error.InvalidIncrementalTestIndex;
-
-                it.end += it.index + 1;
-                break;
-            }
-        } else {
-            it.end += remaining.len;
-        }
-    }
-
-    /// In the event of an `error.InvalidIncrementalTestIndex`, this function can
-    /// be used to find the current filename that was being processed.
-    /// Asserts the iterator hasn't reached the end.
-    fn currentFilename(it: TestIterator) []const u8 {
-        assert(it.end != it.filenames.len);
-        const remaining = it.filenames[it.end..];
-        return remaining[it.index + 1];
-    }
-};
-
-/// For a filename in the format "<filename>.X.<ext>" or "<filename>.<ext>", returns
-/// "<filename>", "<ext>" and X parsed as a decimal number. If X is not present, or
-/// cannot be parsed as a decimal number, it is treated as part of <filename>
-fn getTestFileNameParts(name: []const u8) struct {
-    base_name: []const u8,
-    file_ext: []const u8,
-    test_index: ?usize,
-} {
-    const file_ext = std.fs.path.extension(name);
-    const trimmed = name[0 .. name.len - file_ext.len]; // Trim off ".<ext>"
-    const maybe_index = std.fs.path.extension(trimmed); // Extract ".X"
-
-    // Attempt to parse index
-    const index: ?usize = if (maybe_index.len > 0)
-        std.fmt.parseInt(usize, maybe_index[1..], 10) catch null
-    else
-        null;
-
-    // Adjust "<filename>" extent based on parsing success
-    const base_name_end = trimmed.len - if (index != null) maybe_index.len else 0;
-    return .{
-        .base_name = name[0..base_name_end],
-        .file_ext = if (file_ext.len > 0) file_ext[1..] else file_ext,
-        .test_index = index,
-    };
-}
-
-const TestStrategy = enum {
-    /// Execute tests as independent compilations, unless they are explicitly
-    /// incremental ("foo.0.zig", "foo.1.zig", etc.)
-    independent,
-    /// Execute all tests as incremental updates to a single compilation. Explicitly
-    /// incremental tests ("foo.0.zig", "foo.1.zig", etc.) still execute in order
-    incremental,
-};
-
 /// Default config values for known test manifest key-value pairings.
 /// Currently handled defaults are:
 /// * backend