test: gate firecracker fork tests behind linux build tag

The two TestForkFirecracker* tests invoke forkInstanceFromStoppedOrStandby
which needs a hypervisor VM starter — firecracker is linux-only, so these
fail on darwin with 'no VM starter for hypervisor type: firecracker'.

Split into _linux_test.go; leave the pure-helper TestInstallForkSharedMemFile_*
tests cross-platform.

Author: sjmiller609

lib/instances/templates_shared_memfile_linux_test.go

@@ -0,0 +1,84 @@
+//go:build linux
+
+package instances
+
+import (
+	"context"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/kernel/hypeman/lib/hypervisor"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// TestForkFirecrackerSharesMemFile_FromTemplate verifies the end-to-end fork
+// path: when the source is a Firecracker Template instance, the fork's
+// mem-file is a hardlink to the source's mem-file instead of a copy. This
+// preserves the firecracker MAP_PRIVATE COW semantics that let multiple forks
+// share the heavy backing file.
+func TestForkFirecrackerSharesMemFile_FromTemplate(t *testing.T) {
+	t.Parallel()
+
+	mgr, _ := setupTestManager(t)
+	ctx := context.Background()
+
+	sourceID := "shared-memfile-fc-src"
+	createStandbySnapshotSourceFixture(t, mgr, sourceID, "shared-memfile-fc-src", hypervisor.TypeFirecracker)
+	promoteFixtureToTemplate(t, mgr, sourceID)
+
+	srcSnapshotDir := mgr.paths.InstanceSnapshotLatest(sourceID)
+	srcMem := filepath.Join(srcSnapshotDir, templateSharedMemFileName)
+	require.NoError(t, os.WriteFile(srcMem, []byte("firecracker mem-file contents"), 0o644))
+	snapshotConfigPath := mgr.paths.InstanceSnapshotConfig(sourceID)
+	require.NoError(t, os.MkdirAll(filepath.Dir(snapshotConfigPath), 0o755))
+	require.NoError(t, os.WriteFile(snapshotConfigPath, []byte(`{}`), 0o644))
+
+	forked, err := mgr.forkInstanceFromStoppedOrStandby(ctx, sourceID, ForkInstanceRequest{
+		Name:        "shared-memfile-fc-fork",
+		TargetState: StateStopped,
+	}, true)
+	require.NoError(t, err)
+	require.NotNil(t, forked)
+
+	forkMem := filepath.Join(mgr.paths.InstanceSnapshotLatest(forked.Id), templateSharedMemFileName)
+	info, err := os.Lstat(forkMem)
+	require.NoError(t, err)
+	assert.True(t, info.Mode().IsRegular(), "fork mem-file must be a regular file (hardlink) for firecracker fan-out")
+	assert.True(t, sameInode(t, srcMem, forkMem), "fork mem-file must share the source's inode")
+}
+
+// TestForkFirecrackerStandbySourceDoesNotShareMemFile guards the
+// non-Template carve-out: forking a plain Standby source must copy the
+// mem-file outright. Sharing would let a later RestoreInstance on the source
+// mutate the file out from under live forks.
+func TestForkFirecrackerStandbySourceDoesNotShareMemFile(t *testing.T) {
+	t.Parallel()
+
+	mgr, _ := setupTestManager(t)
+	ctx := context.Background()
+
+	sourceID := "standby-fork-fc-src"
+	createStandbySnapshotSourceFixture(t, mgr, sourceID, "standby-fork-fc-src", hypervisor.TypeFirecracker)
+
+	srcSnapshotDir := mgr.paths.InstanceSnapshotLatest(sourceID)
+	srcMem := filepath.Join(srcSnapshotDir, templateSharedMemFileName)
+	require.NoError(t, os.WriteFile(srcMem, []byte("firecracker mem-file contents"), 0o644))
+	snapshotConfigPath := mgr.paths.InstanceSnapshotConfig(sourceID)
+	require.NoError(t, os.MkdirAll(filepath.Dir(snapshotConfigPath), 0o755))
+	require.NoError(t, os.WriteFile(snapshotConfigPath, []byte(`{}`), 0o644))
+
+	forked, err := mgr.forkInstanceFromStoppedOrStandby(ctx, sourceID, ForkInstanceRequest{
+		Name:        "standby-fork-fc-fork",
+		TargetState: StateStopped,
+	}, true)
+	require.NoError(t, err)
+	require.NotNil(t, forked)
+
+	forkMem := filepath.Join(mgr.paths.InstanceSnapshotLatest(forked.Id), templateSharedMemFileName)
+	info, err := os.Lstat(forkMem)
+	require.NoError(t, err)
+	require.True(t, info.Mode().IsRegular(), "standby-source fork mem-file must be a regular file copy")
+	assert.False(t, sameInode(t, srcMem, forkMem), "standby-source fork mem-file must be a copy, not a hardlink to source")
+}

lib/instances/templates_shared_memfile_test.go

@@ -1,13 +1,11 @@
 package instances
 
 import (
-	"context"
 	"os"
 	"path/filepath"
 	"syscall"
 	"testing"
 
-	"github.com/kernel/hypeman/lib/hypervisor"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
@@ -61,76 +59,6 @@ func TestInstallForkSharedMemFile_ErrorsWhenSourceMissing(t *testing.T) {
 	require.Error(t, err)
 }
 
-// TestForkFirecrackerSharesMemFile_FromTemplate verifies the end-to-end fork
-// path: when the source is a Firecracker Template instance, the fork's
-// mem-file is a hardlink to the source's mem-file instead of a copy. This
-// preserves the firecracker MAP_PRIVATE COW semantics that let multiple forks
-// share the heavy backing file.
-func TestForkFirecrackerSharesMemFile_FromTemplate(t *testing.T) {
-	t.Parallel()
-
-	mgr, _ := setupTestManager(t)
-	ctx := context.Background()
-
-	sourceID := "shared-memfile-fc-src"
-	createStandbySnapshotSourceFixture(t, mgr, sourceID, "shared-memfile-fc-src", hypervisor.TypeFirecracker)
-	promoteFixtureToTemplate(t, mgr, sourceID)
-
-	srcSnapshotDir := mgr.paths.InstanceSnapshotLatest(sourceID)
-	srcMem := filepath.Join(srcSnapshotDir, templateSharedMemFileName)
-	require.NoError(t, os.WriteFile(srcMem, []byte("firecracker mem-file contents"), 0o644))
-	snapshotConfigPath := mgr.paths.InstanceSnapshotConfig(sourceID)
-	require.NoError(t, os.MkdirAll(filepath.Dir(snapshotConfigPath), 0o755))
-	require.NoError(t, os.WriteFile(snapshotConfigPath, []byte(`{}`), 0o644))
-
-	forked, err := mgr.forkInstanceFromStoppedOrStandby(ctx, sourceID, ForkInstanceRequest{
-		Name:        "shared-memfile-fc-fork",
-		TargetState: StateStopped,
-	}, true)
-	require.NoError(t, err)
-	require.NotNil(t, forked)
-
-	forkMem := filepath.Join(mgr.paths.InstanceSnapshotLatest(forked.Id), templateSharedMemFileName)
-	info, err := os.Lstat(forkMem)
-	require.NoError(t, err)
-	assert.True(t, info.Mode().IsRegular(), "fork mem-file must be a regular file (hardlink) for firecracker fan-out")
-	assert.True(t, sameInode(t, srcMem, forkMem), "fork mem-file must share the source's inode")
-}
-
-// TestForkFirecrackerStandbySourceDoesNotShareMemFile guards the
-// non-Template carve-out: forking a plain Standby source must copy the
-// mem-file outright. Sharing would let a later RestoreInstance on the source
-// mutate the file out from under live forks.
-func TestForkFirecrackerStandbySourceDoesNotShareMemFile(t *testing.T) {
-	t.Parallel()
-
-	mgr, _ := setupTestManager(t)
-	ctx := context.Background()
-
-	sourceID := "standby-fork-fc-src"
-	createStandbySnapshotSourceFixture(t, mgr, sourceID, "standby-fork-fc-src", hypervisor.TypeFirecracker)
-
-	srcSnapshotDir := mgr.paths.InstanceSnapshotLatest(sourceID)
-	srcMem := filepath.Join(srcSnapshotDir, templateSharedMemFileName)
-	require.NoError(t, os.WriteFile(srcMem, []byte("firecracker mem-file contents"), 0o644))
-	snapshotConfigPath := mgr.paths.InstanceSnapshotConfig(sourceID)
-	require.NoError(t, os.MkdirAll(filepath.Dir(snapshotConfigPath), 0o755))
-	require.NoError(t, os.WriteFile(snapshotConfigPath, []byte(`{}`), 0o644))
-
-	forked, err := mgr.forkInstanceFromStoppedOrStandby(ctx, sourceID, ForkInstanceRequest{
-		Name:        "standby-fork-fc-fork",
-		TargetState: StateStopped,
-	}, true)
-	require.NoError(t, err)
-	require.NotNil(t, forked)
-
-	forkMem := filepath.Join(mgr.paths.InstanceSnapshotLatest(forked.Id), templateSharedMemFileName)
-	info, err := os.Lstat(forkMem)
-	require.NoError(t, err)
-	require.True(t, info.Mode().IsRegular(), "standby-source fork mem-file must be a regular file copy")
-	assert.False(t, sameInode(t, srcMem, forkMem), "standby-source fork mem-file must be a copy, not a hardlink to source")
-}
-
 // promoteFixtureToTemplate marks the source's stored metadata as a Template
 // without invoking the full PromoteToTemplate lifecycle (which would require
 // a live VM). Test-only shortcut.