Adds a test for #240

tests/config.rs

@@ -0,0 +1,44 @@
+extern crate mdbook;
+extern crate tempdir;
+
+use std::path::Path;
+use std::fs::File;
+use std::io::Write;
+
+use mdbook::MDBook;
+use tempdir::TempDir;
+
+// Tests that config values unspecified in the configuration file do not overwrite
+// values specified earlier.
+#[test]
+fn do_not_overwrite_unspecified_config_values() {
+    let dir = TempDir::new("mdbook").expect("Could not create a temp dir");
+    
+    let book = MDBook::new(dir.path())
+        .with_source(Path::new("bar"))
+        .with_destination(Path::new("baz"));
+
+    assert_eq!(book.get_root(), dir.path());
+    assert_eq!(book.get_source(), dir.path().join("bar"));
+    assert_eq!(book.get_destination().unwrap(), dir.path().join("baz"));
+
+    // Test when trying to read a config file that does not exist
+    let book = book.read_config().expect("Error reading the config file");
+
+    assert_eq!(book.get_root(), dir.path());
+    assert_eq!(book.get_source(), dir.path().join("bar"));
+    assert_eq!(book.get_destination().unwrap(), dir.path().join("baz"));
+
+    // Try with a partial config file
+    let file_path = dir.path().join("book.toml");
+    let mut f = File::create(file_path).expect("Could not create config file");
+    f.write_all(br#"source = "barbaz""#).expect("Could not write to config file");
+    f.sync_all().expect("Could not sync the file");
+
+    let book = book.read_config().expect("Error reading the config file");
+
+    assert_eq!(book.get_root(), dir.path());
+    assert_eq!(book.get_source(), dir.path().join("barbaz"));
+    assert_eq!(book.get_destination().unwrap(), dir.path().join("baz"));
+}
+