Added FileList test (DOI-USGS#3168)

* Added LineEqationTests.cpp

* Added FileListTests.cpp
Implemented an istream constructor in FileList.cpp to help with testing.

* added FileList tests. implemented istream constructor for FileList.cpp to help with testing.

* fixed whitespace issues in FileListTests.cpp

* Update FileListTests.cpp

isis/src/base/objs/FileList/FileList.cpp

@@ -48,6 +48,15 @@ namespace Isis {
     read(listFile);
   }
 
+  /**
+   * Constructs a FileList from an istream.
+   *
+   * @param in the istream to read from
+   */
+  FileList::FileList(std::istream &in) {
+    read(in);
+  }
+
 
   /**
    * Opens and loads the list of files from a file.

isis/tests/FileListTests.cpp

@@ -0,0 +1,47 @@
+#include <gtest/gtest.h>
+#include <iostream>
+#include "FileList.h"
+#include "IException.h"
+
+TEST(FileList, NonExistantFileConstructor)
+{
+  try
+  {
+    Isis::FileList fl1(Isis::FileName("FakeFile"));
+  }
+  catch(Isis::IException &e)
+  {
+    EXPECT_TRUE(e.toString().toLatin1().contains("Unable to open [FakeFile]."))
+      << e.toString().toStdString();
+  }
+  catch(...)
+  {
+    FAIL() << "Expected an IException\"Unable to open [FakeFile].\"";
+  }
+}
+
+TEST(FileList, FileNameConstructor)
+{
+  std::istringstream input(
+  "/usgs/pkgs/isis3/isis/src/base/objs/FileList/FileList.cpp\n"
+  "/usgs/pkgs/isis3/isis/src/base/objs/FileList/FileList.h\n"
+  "#Comment\n"
+  "unitTest.cpp\n"
+  ">This will not be comment ignored\n"
+  "\n"
+  "^is a blank line, this line will not be ignored as a comment\n"
+  "  Makefile\n"
+  "  //Testing comment with prepended spaces\n"
+  "\n"
+  "#Above and below are for testing multiple blank lines\n"
+  "\n"
+  "\n"
+  "FileList.h\n");
+  std::ostringstream output;
+  std::string expectedOutput = "/usgs/pkgs/isis3/isis/src/base/objs/FileList/FileList.cpp\n"
+     "/usgs/pkgs/isis3/isis/src/base/objs/FileList/FileList.h\n"
+     "unitTest.cpp\n>This\n^is\nMakefile\nFileList.h\n";
+  Isis::FileList fl1(input);
+  fl1.write(output);
+  EXPECT_STREQ(expectedOutput.c_str(), output.str().c_str());
+}