set a bazel test timeout of 15min
diff --git a/buildkite/pipelines/bazel-postsubmit.json b/buildkite/pipelines/bazel-postsubmit.json
index bb5f893..8052899 100644
--- a/buildkite/pipelines/bazel-postsubmit.json
+++ b/buildkite/pipelines/bazel-postsubmit.json
@@ -6,6 +6,7 @@
         "rm -f WORKSPACE.bak"
       ],
       "build_targets": ["//src:bazel"],
+      "test_flags": ["--test_timeout=900"],
       "test_targets": [
         "//scripts/...",
 	"//src/test/...",
@@ -18,6 +19,7 @@
         "rm -f WORKSPACE.bak"
       ],
       "build_targets": ["//src:bazel"],
+      "test_flags": ["--test_timeout=900"],
       "test_targets": [
         "//scripts/...",
 	"//src/test/...",
@@ -30,6 +32,7 @@
         "rm -f WORKSPACE.bak"
       ],
       "build_targets": ["//src:bazel"],
+      "test_flags": ["--test_timeout=900"],
       "test_targets": [
         "//scripts/...",
 	"//src/test/...",