improve Makefile tests

.docker/Dockerfile_pre_test

@@ -1,9 +1,20 @@
 FROM rust:1.58-buster
 
 RUN apt update
-RUN apt install -y libglib2.0-dev libgtk-3-dev libsoup2.4-dev libappindicator3-dev libwebkit2gtk-4.0-dev firefox-esr
+RUN apt install -y \
+    libglib2.0-dev \
+    libgtk-3-dev \
+    libsoup2.4-dev \
+    libappindicator3-dev \
+    libwebkit2gtk-4.0-dev \
+    firefox-esr
+# for kcov and Tarpaulin
+#liblzma-dev binutils-dev libcurl4-openssl-dev libdw-dev libelf-dev
 
 RUN cargo install cargo-make --debug
+# for test coverage
+#RUN cargo install cargo-tarpaulin
+# clean up a bit
 RUN cargo install cargo-cache && cargo cache -a
 
-CMD ["echo","\"base image built\""]
+CMD ["exit"]