*: refactor methods to support mocking

Additionally, write some tests to ensure the driver method
`startBlacksmithBuilder` handles all exceptions correctly in
both nofallback=true and nofallback=false configurations.

package-lock.json

@@ -15,6 +15,7 @@
         "portfinder": "^1.0.32"
       },
       "devDependencies": {
+        "@types/jest": "^29.5.14",
         "@types/node": "^20.12.12",
         "@typescript-eslint/eslint-plugin": "^7.9.0",
         "@typescript-eslint/parser": "^7.9.0",
@@ -25,7 +26,7 @@
         "eslint-plugin-prettier": "^5.1.3",
         "jest": "^29.7.0",
         "prettier": "^3.2.5",
-        "ts-jest": "^29.1.2",
+        "ts-jest": "^29.2.5",
         "ts-node": "^10.9.2",
         "typescript": "^5.4.5"
       }
@@ -2208,6 +2209,16 @@
         "@types/istanbul-lib-report": "*"
       }
     },
+    "node_modules/@types/jest": {
+      "version": "29.5.14",
+      "resolved": "https://registry.npmjs.org/@types/jest/-/jest-29.5.14.tgz",
+      "integrity": "sha512-ZN+4sdnLUbo8EVvVc2ao0GFW6oVrQRPn4K2lglySj7APvSrgzxHiNNK99us4WDMi57xxA2yggblIAMNhXOotLQ==",
+      "dev": true,
+      "dependencies": {
+        "expect": "^29.0.0",
+        "pretty-format": "^29.0.0"
+      }
+    },
     "node_modules/@types/node": {
       "version": "20.16.5",
       "resolved": "https://registry.npmjs.org/@types/node/-/node-20.16.5.tgz",