From 0c80404e1140b19576505c3cf4416cad56400d29 Mon Sep 17 00:00:00 2001
From: Julien Dessaux
Date: Sun, 20 Feb 2022 23:05:50 +0100
Subject: Added code coverage to tests with zig build test -Dtest-coverage

---
 .gitignore |  1 +
 build.zig  | 21 +++++++++++++++++++++
 2 files changed, 22 insertions(+)

diff --git a/.gitignore b/.gitignore
index 4c82b07..6380ab0 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,3 @@
+kcov-output/
 zig-cache
 zig-out
diff --git a/build.zig b/build.zig
index 556896e..799aebb 100644
--- a/build.zig
+++ b/build.zig
@@ -22,6 +22,8 @@ pub fn build(b: *std.build.Builder) void {
         run_cmd.addArgs(args);
     }
 
+    const coverage = b.option(bool, "test-coverage", "Generate test coverage") orelse false;
+
     const run_step = b.step("run", "Run the app");
     run_step.dependOn(&run_cmd.step);
 
@@ -29,6 +31,25 @@ pub fn build(b: *std.build.Builder) void {
     exe_tests.setTarget(target);
     exe_tests.setBuildMode(mode);
 
+    // Code coverage with kcov, we need an allocator for the setup
+    var general_purpose_allocator = std.heap.GeneralPurposeAllocator(.{}){};
+    defer _ = general_purpose_allocator.deinit();
+    const gpa = general_purpose_allocator.allocator();
+    // We want to exclude the $HOME/.zig path
+    const home = std.process.getEnvVarOwned(gpa, "HOME") catch "";
+    defer gpa.free(home);
+    const exclude = std.fmt.allocPrint(gpa, "--exclude-path={s}/.zig/", .{home}) catch "";
+    defer gpa.free(exclude);
+    if (coverage) {
+        exe_tests.setExecCmd(&[_]?[]const u8{
+            "kcov",
+            exclude,
+            //"--path-strip-level=3", // any kcov flags can be specified here
+            "kcov-output", // output dir for kcov
+            null, // to get zig to use the --test-cmd-bin flag
+        });
+    }
+
     const test_step = b.step("test", "Run unit tests");
     test_step.dependOn(&exe_tests.step);
 }
-- 
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