diff --git a/.gitignore b/.gitignore
index 9affdae..79aa481 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,5 +1,6 @@
 .zig-cache/
 zig-out/
+coverage/
 .env
 *.srf
 !metadata.srf
diff --git a/build.zig b/build.zig
index f4fb4e7..13f6275 100644
--- a/build.zig
+++ b/build.zig
@@ -1,4 +1,5 @@
 const std = @import("std");
+const Coverage = @import("build/Coverage.zig");
 
 pub fn build(b: *std.Build) void {
     const target = b.standardTargetOptions(.{});
@@ -106,4 +107,7 @@ pub fn build(b: *std.Build) void {
         .install_dir = .prefix,
         .install_subdir = "docs",
     }).step);
+
+    // Coverage: `zig build coverage` (Linux only, uses kcov)
+    _ = Coverage.addCoverageStep(b, mod, "zfin");
 }
diff --git a/build/Coverage.zig b/build/Coverage.zig
new file mode 100644
index 0000000..a0c97e9
--- /dev/null
+++ b/build/Coverage.zig
@@ -0,0 +1,182 @@
+const builtin = @import("builtin");
+const std = @import("std");
+const Build = std.Build;
+
+const Coverage = @This();
+
+/// Adds test coverage. This will create a new test coverage executable to the
+/// build graph, generated only if coverage is a target. It will create an
+/// option -Dcoverage-threshold that will fail the build if the threshold is
+/// not met. It will also add a step that downloads a zig fork of the kcov
+/// executable into zig cache if it doesn't already exist
+///
+/// Because it is creating a new test executable from the root module provided,
+/// if there are any linking steps being done to your test executable, those
+/// must also be done to the test_exe returned by this function
+pub fn addCoverageStep(b: *Build, root_module: *Build.Module, coverage_name: []const u8) *Coverage {
+    //verify host requirements
+    {
+        const supported = builtin.os.tag == .linux and
+            (builtin.cpu.arch == .x86_64 or builtin.cpu.arch == .aarch64);
+
+        if (!supported)
+            @panic("Coverage only supported on x86_64-linux or aarch64-linux");
+    }
+
+    // Add options
+    const coverage_threshold = b.option(u7, "coverage-threshold", "Minimum coverage percentage required") orelse 0;
+    const coverage_dir = b.option([]const u8, "coverage-dir", "Coverage output directory") orelse
+        b.pathJoin(&.{ b.build_root.path orelse ".", "coverage" });
+    const coverage_step = b.step("coverage", "Generate test coverage report");
+
+    // Set up kcov download
+    // We can't do it directly because we are sandboxed during build, but
+    // we can create a program and run that program. First we need the destination
+    // directory
+    const kcov = blk: {
+        const arch_name = switch (builtin.cpu.arch) {
+            .x86_64 => "x86_64",
+            .aarch64 => "aarch64",
+            else => unreachable,
+        };
+
+        const Algo = std.crypto.hash.sha2.Sha256;
+        var hasher = Algo.init(.{});
+        hasher.update("kcov-");
+        hasher.update(arch_name);
+        var cache_hash: [Algo.digest_length]u8 = undefined;
+        hasher.final(&cache_hash);
+
+        const cache_dir = b.pathJoin(&.{
+            b.cache_root.path.?,
+            "o",
+            b.fmt("{s}", .{std.fmt.bytesToHex(cache_hash, .lower)}),
+        });
+
+        const kcov_name = b.fmt("kcov-{s}", .{arch_name});
+        break :blk .{ .path = b.pathJoin(&.{ cache_dir, kcov_name }), .arch = arch_name };
+    };
+
+    // Create download and coverage build steps
+    return blk: {
+        const download_exe = b.addExecutable(.{
+            .name = "download-kcov",
+            .root_module = b.createModule(.{
+                .root_source_file = b.path("build/download_kcov.zig"),
+                .target = b.resolveTargetQuery(.{}),
+            }),
+        });
+
+        const run_download = b.addRunArtifact(download_exe);
+        run_download.addArg(kcov.path);
+        run_download.addArg(kcov.arch);
+
+        const run_coverage = b.addSystemCommand(&.{kcov.path});
+        const include_path = b.pathJoin(&.{ b.build_root.path.?, "src" });
+        run_coverage.addArgs(&.{ "--include-path", include_path });
+        const css_file = b.pathJoin(&.{ b.build_root.path.?, "build", "bcov.css" });
+        run_coverage.addArg(b.fmt("--configure=css-file={s}", .{css_file}));
+        run_coverage.addArg(coverage_dir);
+        const test_exe = b.addTest(.{
+            .name = coverage_name,
+            .root_module = root_module,
+            // we need to set the test exe to use llvm as the self hosted backend
+            // does not support the data kcov needs
+            .use_llvm = true,
+        });
+        run_coverage.addArtifactArg(test_exe);
+        run_coverage.step.dependOn(&test_exe.step);
+        run_coverage.step.dependOn(&run_download.step);
+
+        const json_path = b.fmt("{s}/{s}/coverage.json", .{ coverage_dir, coverage_name });
+        const verbose = b.option(bool, "coverage-verbose", "Show test coverage for each file") orelse false;
+        const check_step = create(b, test_exe, json_path, coverage_threshold, verbose);
+        check_step.step.dependOn(&run_coverage.step);
+        coverage_step.dependOn(&check_step.step);
+        break :blk check_step;
+    };
+}
+
+step: Build.Step,
+json_path: []const u8,
+threshold: u7,
+test_exe: *std.Build.Step.Compile,
+verbose: bool,
+
+pub fn create(owner: *Build, test_exe: *std.Build.Step.Compile, xml_path: []const u8, threshold: u7, verbose: bool) *Coverage {
+    const check = owner.allocator.create(Coverage) catch @panic("OOM");
+    check.* = .{
+        .step = Build.Step.init(.{
+            .id = .custom,
+            .name = "check coverage",
+            .owner = owner,
+            .makeFn = make,
+        }),
+        .json_path = xml_path,
+        .threshold = threshold,
+        .test_exe = test_exe,
+        .verbose = verbose,
+    };
+    return check;
+}
+
+// This must be kept in step with kcov coverage.json format
+const CoverageReport = struct {
+    percent_covered: f64,
+    covered_lines: usize,
+    total_lines: usize,
+    percent_low: u7,
+    percent_high: u7,
+    command: []const u8,
+    date: []const u8,
+    files: []File,
+};
+
+const File = struct {
+    file: []const u8,
+    percent_covered: f64,
+    covered_lines: usize,
+    total_lines: usize,
+
+    pub fn coverageLessThanDesc(context: []File, lhs: File, rhs: File) bool {
+        _ = context;
+        return lhs.percent_covered > rhs.percent_covered;
+    }
+};
+
+fn make(step: *Build.Step, options: Build.Step.MakeOptions) !void {
+    _ = options;
+    const check: *Coverage = @fieldParentPtr("step", step);
+    const allocator = step.owner.allocator;
+
+    const file = try std.fs.cwd().openFile(check.json_path, .{});
+    defer file.close();
+
+    const content = try file.readToEndAlloc(allocator, 10 * 1024 * 1024);
+    defer allocator.free(content);
+
+    const json = try std.json.parseFromSlice(CoverageReport, allocator, content, .{});
+    defer json.deinit();
+    const coverage = json.value;
+
+    var stdout_buffer: [1024]u8 = undefined;
+    var stdout_writer = std.fs.File.stdout().writer(&stdout_buffer);
+    const stdout = &stdout_writer.interface;
+    if (step.owner.verbose or check.verbose) {
+        const files = coverage.files;
+        std.mem.sort(File, files, files, File.coverageLessThanDesc);
+        for (files) |f|
+            try stdout.print(
+                "{d: >5.1}% {d: >5}/{d: <5}:{s}\n",
+                .{ f.percent_covered, f.covered_lines, f.total_lines, f.file },
+            );
+    }
+    try stdout.print(
+        "Total test coverage: {d}% ({d}/{d})\n",
+        .{ coverage.percent_covered, coverage.covered_lines, coverage.total_lines },
+    );
+    try stdout.flush();
+
+    if (@as(u7, @intFromFloat(@floor(coverage.percent_covered))) < check.threshold)
+        return step.fail("Coverage {d}% is below threshold {d}%", .{ coverage.percent_covered, check.threshold });
+}
diff --git a/build/bcov.css b/build/bcov.css
new file mode 100644
index 0000000..861cfb1
--- /dev/null
+++ b/build/bcov.css
@@ -0,0 +1,46 @@
+/* Based upon the lcov CSS style, style files can be reused - Dark Theme */
+body { color: #e0e0e0; background-color: #1e1e1e; }
+a:link { color: #6b9aff; text-decoration: underline; }
+a:visited { color: #4dbb7a; text-decoration: underline; }
+a:active { color: #ff6b8a; text-decoration: underline; }
+td.title { text-align: center; padding-bottom: 10px; font-size: 20pt; font-weight: bold; }
+td.ruler { background-color: #4a6ba8; }
+td.headerItem { text-align: right; padding-right: 6px; font-family: sans-serif; font-weight: bold; }
+td.headerValue { text-align: left; color: #6b9aff; font-family: sans-serif; font-weight: bold; }
+td.versionInfo { text-align: center; padding-top:  2px; }
+th.headerItem { text-align: right; padding-right: 6px; font-family: sans-serif; font-weight: bold; }
+th.headerValue { text-align: left; color: #6b9aff; font-family: sans-serif; font-weight: bold; }
+pre.source { font-family: monospace; white-space: pre; overflow: hidden; text-overflow: ellipsis; }
+span.lineNum { background-color: #5a5a2a; }
+span.lineNumLegend { background-color: #5a5a2a; width: 96px; font-weight: bold ;}
+span.lineCov { background-color: #2d5a2d; }
+span.linePartCov { background-color: #707000; }
+span.lineNoCov { background-color: #762c2c; }
+span.orderNum { background-color: #5a4a2a; float: right; width:5em; text-align: left; }
+span.orderNumLegend { background-color: #5a4a2a; width: 96px; font-weight: bold ;}
+span.coverHits { background-color: #4a4a2a;  padding-left: 3px; padding-right: 1px;  text-align: right; list-style-type: none; display: inline-block; width: 5em; }
+span.coverHitsLegend { background-color: #4a4a2a; width: 96px; font-weight: bold; margin: 0 auto;}
+td.tableHead { text-align: center; color: #e0e0e0; background-color: #4a6ba8; font-family: sans-serif; font-size: 120%; font-weight: bold; }
+td.coverFile { text-align: left; padding-left: 10px; padding-right: 20px; color: #6b9aff; font-family: monospace; background-color: #3a3a3a; }
+td.coverBar { padding-left: 10px; padding-right: 10px; background-color: #3a3a3a; }
+td.coverBarOutline { background-color: #4a4a4a; }
+td.coverPer { text-align: left; padding-left: 10px; padding-right: 10px; font-weight: bold; background-color: #3a3a3a; color: #e0e0e0; }
+td.coverPerLeftMed { text-align: left; padding-left: 10px; padding-right: 10px; background-color: #5a5a00; font-weight: bold; color: #e0e0e0; }
+td.coverPerLeftLo { text-align: left; padding-left: 10px; padding-right: 10px; background-color: #5a2d2d; font-weight: bold; color: #e0e0e0; }
+td.coverPerLeftHi { text-align: left; padding-left: 10px; padding-right: 10px; background-color: #2d5a2d; font-weight: bold; color: #e0e0e0; }
+td.coverNum { text-align: right; padding-left: 10px; padding-right: 10px; background-color: #3a3a3a; color: #e0e0e0; }
+
+/* Override tablesorter hover styles for dark theme */
+.tablesorter-blue tbody > tr:hover > td,
+.tablesorter-blue tbody > tr:hover + tr.tablesorter-childRow > td,
+.tablesorter-blue tbody > tr:hover + tr.tablesorter-childRow + tr.tablesorter-childRow > td,
+.tablesorter-blue tbody > tr.even:hover > td,
+.tablesorter-blue tbody > tr.even:hover + tr.tablesorter-childRow > td,
+.tablesorter-blue tbody > tr.even:hover + tr.tablesorter-childRow + tr.tablesorter-childRow > td {
+	background: #4a4a4a;
+}
+.tablesorter-blue tbody > tr.odd:hover > td,
+.tablesorter-blue tbody > tr.odd:hover + tr.tablesorter-childRow > td,
+.tablesorter-blue tbody > tr.odd:hover + tr.tablesorter-childRow + tr.tablesorter-childRow > td {
+	background: #4a4a4a;
+}
diff --git a/build/download_kcov.zig b/build/download_kcov.zig
new file mode 100644
index 0000000..f04c85a
--- /dev/null
+++ b/build/download_kcov.zig
@@ -0,0 +1,82 @@
+const std = @import("std");
+
+pub fn main() !void {
+    var gpa = std.heap.GeneralPurposeAllocator(.{}){};
+    const allocator = gpa.allocator();
+
+    const args = try std.process.argsAlloc(allocator);
+    defer std.process.argsFree(allocator, args);
+
+    if (args.len != 3) return error.InvalidArgs;
+
+    const kcov_path = args[1];
+    const arch_name = args[2];
+
+    // Check to see if file exists. If it does, we have nothing more to do
+    const stat = std.fs.cwd().statFile(kcov_path) catch |err| blk: {
+        if (err == error.FileNotFound) break :blk null else return err;
+    };
+    // This might be better checking whether it's executable and >= 7MB, but
+    // for now, we'll do a simple exists check
+    if (stat != null) return;
+    var stdout_buffer: [1024]u8 = undefined;
+    var stdout_writer = std.fs.File.stdout().writer(&stdout_buffer);
+    const stdout = &stdout_writer.interface;
+
+    try stdout.writeAll("Determining latest kcov version\n");
+    try stdout.flush();
+
+    var client = std.http.Client{ .allocator = allocator };
+    defer client.deinit();
+
+    // Get redirect to find latest version
+    const list_uri = try std.Uri.parse("https://git.lerch.org/lobo/-/packages/generic/kcov/");
+    var req = try client.request(.GET, list_uri, .{ .redirect_behavior = .unhandled });
+    defer req.deinit();
+
+    try req.sendBodiless();
+    var redirect_buf: [1024]u8 = undefined;
+    const response = try req.receiveHead(&redirect_buf);
+
+    if (response.head.status != .see_other) return error.UnexpectedResponse;
+
+    const location = response.head.location orelse return error.NoLocation;
+    const version_start = std.mem.lastIndexOf(u8, location, "/") orelse return error.InvalidLocation;
+    const version = location[version_start + 1 ..];
+
+    try stdout.print(
+        "Downloading kcov version {s} for {s} to {s}...",
+        .{ version, arch_name, kcov_path },
+    );
+    try stdout.flush();
+
+    const binary_url = try std.fmt.allocPrint(
+        allocator,
+        "https://git.lerch.org/api/packages/lobo/generic/kcov/{s}/kcov-{s}",
+        .{ version, arch_name },
+    );
+    defer allocator.free(binary_url);
+
+    const cache_dir = std.fs.path.dirname(kcov_path) orelse return error.InvalidPath;
+    std.fs.cwd().makeDir(cache_dir) catch |e| switch (e) {
+        error.PathAlreadyExists => {},
+        else => return e,
+    };
+
+    const uri = try std.Uri.parse(binary_url);
+    const file = try std.fs.cwd().createFile(kcov_path, .{ .mode = 0o755 });
+    defer file.close();
+
+    var buffer: [8192]u8 = undefined;
+    var writer = file.writer(&buffer);
+    const result = try client.fetch(.{
+        .location = .{ .uri = uri },
+        .response_writer = &writer.interface,
+    });
+
+    if (result.status != .ok) return error.DownloadFailed;
+    try writer.interface.flush();
+
+    try stdout.writeAll("done\n");
+    try stdout.flush();
+}