test(devtools): create unit tests for injector tree transformation fu…

…nctions

Creates set of unit tests for each function in the data transformation pipeline that enables injector metadata to be visualized as d3 graphs.

devtools/projects/ng-devtools/src/lib/devtools-tabs/injector-tree/BUILD.bazel

@@ -1,5 +1,7 @@
 load("//devtools/tools:ng_module.bzl", "ng_module")
 load("@io_bazel_rules_sass//:defs.bzl", "sass_binary")
+load("//devtools/tools:typescript.bzl", "ts_test_library")
+load("//devtools/tools:defaults.bzl", "karma_web_test_suite")
 
 package(default_visibility = ["//:__subpackages__"])
 
@@ -46,3 +48,19 @@ ng_module(
         "@npm//@angular/material",
     ],
 )
+
+ts_test_library(
+    name = "injector_tree_test",
+    srcs = ["injector-tree.spec.ts"],
+    deps = [
+        ":injector_tree",
+        "//devtools/projects/ng-devtools/src/lib/devtools-tabs/dependency-injection:injector_tree_visualizer",
+    ],
+)
+
+karma_web_test_suite(
+    name = "test",
+    deps = [
+        ":injector_tree_test",
+    ],
+)