Add googletest.

WORKSPACE.bazel

+workspace(name = "IMGRender")
+
+# Google test for unittest purposes
+load("@bazel_tools//tools/build_defs/repo:git.bzl", "git_repository")
+git_repository(
+    name = "gtest",
+    remote = "https://github.com/google/googletest",
+    branch = "v1.10.x",
+)
+
+# Theft for property-based testing
 new_local_repository(
     name = "theft",
     path = "./external/theft",
     build_file = "BUILDS/BUILD.theft"
 )
+
+

tests/BUILD.bazel

+
+
 # Needed for each target whose artifacts are to be checked.
 cc_test(
     name = "check",
     srcs = ["check.cc"],
     args = ["/home"],
-    deps = ["//src:render", "@theft//:theft",]
+    deps = [
+        "//src:render",
+        "@theft//:theft",
+        "@gtest//:gtest",
+        "@gtest//:gtest_main"
+    ]
 )

tests/check.cc

 #include "src/canvas.h"
+#include "gtest/gtest.h"
 
 extern "C" {
 #include "external/theft/inc/theft.h"
 }
 
-int main(void) {
-    theft_seed_of_time();
-    return say();
+// Tests factorial of 0.
+TEST(FactorialTest, HandlesZeroInput) {
+  EXPECT_EQ(1, 1);
+}
+
+// Tests factorial of positive numbers.
+TEST(FactorialTest, HandlesPositiveInput) {
+  EXPECT_EQ(1, 1);
+  EXPECT_EQ(2, 2);
+  EXPECT_EQ(6, 6);
+  EXPECT_EQ(40320, 40320);
 }