test: add some tests to kick things off

Author: TomerAberbach

src/fixtures/test.json

@@ -0,0 +1,5 @@
+{
+  "dependencies": {
+    "example": "1.0.0"
+  }
+}

src/index.test.ts

@@ -0,0 +1,40 @@
+import test from 'ava'
+import { testProp, fc } from 'ava-fast-check'
+import { Arbitrary } from 'fast-check'
+import { PluginContext, Plugin } from 'rollup'
+import externals, { ExternalsOptions } from './index'
+
+// Returns an arbitrary for generating externals options objects
+const externalsOptionsArbitrary = (): Arbitrary<ExternalsOptions> =>
+    fc.record({
+        packagePath: fc.string(),
+        builtins: fc.boolean(),
+        deps: fc.boolean(),
+        devDeps: fc.boolean(),
+        peerDeps: fc.boolean(),
+        optDeps: fc.boolean(),
+        include: fc.oneof(fc.string(), fc.array(fc.string())),
+        exclude: fc.oneof(fc.string(), fc.array(fc.string())),
+        except: fc.oneof(fc.string(), fc.array(fc.string()))
+    }, { withDeletedKeys: true })
+
+testProp(
+    'does not throw on constructing plugin object for valid input',
+    [externalsOptionsArbitrary()],
+    options => {
+        try {
+            externals(options)
+            return true
+        } catch {
+            return false
+        }
+    }
+)
+
+test('does not mark "dependencies" dependency as external by default', t => {
+    const source = 'example'
+    const importer = 'me'
+    const plugin = externals({ packagePath: './fixtures/test.json' }) as Plugin & PluginContext
+
+    t.is(plugin.resolveId(source, importer), null)
+})