Add a simple test for nix why-depends

tests/dependencies.nix

@@ -27,6 +27,8 @@ let {
     input1 = input1 + "/.";
     input2 = "${input2}/.";
     input1_drv = input1;
+    input2_drv = input2;
+    input0_drv = input0;
     meta.description = "Random test package";
   };
 

tests/local.mk

@@ -61,7 +61,8 @@ nix_tests = \
   ca/concurrent-builds.sh \
   ca/nix-copy.sh \
   eval-store.sh \
-  readfile-context.sh
+  readfile-context.sh \
+  why-depends.sh
   # parallel.sh
 
 ifeq ($(HAVE_LIBCPUID), 1)

tests/why-depends.sh

@@ -0,0 +1,13 @@
+source common.sh
+
+clearStore
+
+cp ./dependencies.nix ./dependencies.builder0.sh ./config.nix $TEST_HOME
+
+cd $TEST_HOME
+
+nix-build ./dependencies.nix -A input0_drv -o dep
+nix-build ./dependencies.nix -o toplevel
+
+nix why-depends ./toplevel ./dep |
+    grep input-2