tests(cli) add tests for nginx binary locator

spec/02-integration/02-cmd/15-utils_spec.lua

@@ -0,0 +1,72 @@
+describe("kong cli utils", function()
+
+  describe("nginx_signals", function()
+    local signals = require "kong.cmd.utils.nginx_signals"
+    local pl_path = require "pl.path"
+    local pl_file = require "pl.file"
+    local pl_dir = require "pl.dir"
+
+    describe("find_nginx_bin()", function()
+      local tmpdir
+      before_each(function()
+        tmpdir = pl_path.tmpname()
+        assert(os.remove(tmpdir))
+      end)
+
+      after_each(function()
+        pcall(pl_dir.rmtree, tmpdir)
+      end)
+
+      local function fake_nginx_binary(version)
+        local bin_dir = pl_path.join(tmpdir, "nginx/sbin")
+        pl_dir.makepath(bin_dir)
+
+        local nginx = pl_path.join(bin_dir, "nginx")
+        pl_file.write(nginx, string.format(
+          [[#!/bin/sh
+echo 'nginx version: openresty/%s' >&2]], version
+        ))
+
+        assert(os.execute("chmod +x " .. nginx))
+
+        return nginx
+      end
+
+
+      it("works with empty/unset input", function()
+        local bin, err = signals.find_nginx_bin()
+        assert.is_nil(err)
+        assert.matches("sbin/nginx", bin)
+        assert.truthy(pl_path.exists(bin))
+      end)
+
+      it("works when openresty_prefix is unset", function()
+        local bin, err = signals.find_nginx_bin({})
+        assert.is_nil(err)
+        assert.matches("sbin/nginx", bin)
+        assert.truthy(pl_path.exists(bin))
+      end)
+
+      it("prefers `openresty_prefix` when supplied", function()
+        local meta = require "kong.meta"
+        local version = meta._DEPENDENCIES.nginx[1]
+
+        local nginx = fake_nginx_binary(version)
+
+        local bin, err = signals.find_nginx_bin({ openresty_prefix = tmpdir })
+
+        assert.is_nil(err)
+        assert.equals(nginx, bin)
+      end)
+
+      it("returns nil+error if a compatible nginx bin is not found in `openresty_prefix`", function()
+        fake_nginx_binary("1.0.1")
+        local bin, err = signals.find_nginx_bin({ openresty_prefix = tmpdir })
+        assert.is_nil(bin)
+        assert.not_nil(err)
+        assert.matches("could not find OpenResty", err)
+      end)
+
+    end)
+  end)
+end)